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NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World

March 6, 2026

NCERT Solutions For Class 10 Science Chapter 11 Human Eye And Colourful World: In this article, you will find out all the necessary information regarding class 10 science chapter 11 NCERT solutions. Practicing NCERT class 10 science chapter 11 notes will help candidates to bag a good score in class 10 board exam. Further having good knowledge of the unit human eye and colorful world class 10 science NCERT Solutions will build a strong foundation in clearing the Engineering competitive exams as this unit comes under the subject Physics.

The questions in each and every exercise of Human Eye and Colourful world comes with the answer and a detailed, step-by-step solution for better understanding by the student. So Read on to find out everything about NCERT Solutions For Class 10 Science Chapter 11 Human Eye And Colourful World to make a good grade in CBSE Class 10 Board exam.

NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World

Before getting into the details of NCERT Solutions For Class 10 Science Chapter 11 Human Eye And Colourful World, let’s have an overview of list of topics and subtopics under class 10 science chapter 11 NCERT solutions:

The Human Eye And The Colourful World
The Human Eye
Defects Of Vision And Their Correction
Refraction Of Light Through A Prism
Dispersion Of White Light By A Glass Prism
Atmospheric Refraction
Scattering Of Light

Free download NCERT Solutions for Class 10 Science Chapter 11 Human Eye And Colourful World PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 11 Intext Questions

Page Number: 190

Question 1
What is meant by power of accommodation of the eye ?
Answer:
The power of accommodation of the eye is the maximum variation of its power for focusing on near and far (distant) objects.

Question 2
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision ?
Answer:
Concave lens.

Question 3
What is the far point and near point of the human eye with normal vision ?
Answer:
For a human eye with normal vision the far point is at infinity and near point is 25 cm from the eye.

Question 4
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from ? How can it be corrected?
Answer:
The child is suffering from myopia. The child should use concave lens of suitable focal length.

NCERT Solutions for Class 10 Science Chapter 11 Textbook Chapter End Questions

Question 1
The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to
(a) presbyopia
(b) accommodation
(c) near – sightedness
(d) far – sightedness
Answer:
(b) Accommodation

Question 2
The human eye forms the image of an object at its
(a) cornea
(b) iris
(c) pupil
(d) retina
Answer:
(d) Retina

Question 3
The least distance of distinct vision for a young adult with normal vision is about
(a) 25 m
(b) 2.5 cm
(c) 25 cm
(d) 2.5 m
Answer:
(c) 25 cm

Question 4
The change in focal length of an eye lens is caused by the action of the
(a) pupil
(b) retina
(c) ciliary muscles
(d) iris
Answer:
(c) Ciliary muscles

Question 5
A person needs a lens of power -5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision ?
Solution:
(i) ∵ Power of distant viewing part of the lens, P₁ = -5.5 D
∴ Focal length of this part, f₁ = \(\frac { 1 }{ { p }_{ 1 } }\) = \(\frac { 1 }{ -5.5 }\) m = -0.182 m = -18.2 cm

(ii) For near vision,

Question 6
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem ?
Solution:
The remedial lens should make the objects at infinity appear at the far point.
Therefore, for object at infinity, u = ∞
Far point distance of the defected eye, ν = – 80 cm

Negative sign shows that the remedial lens is a concave lens.

Question 7
Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye is 1 m. What is the power of the lens required to correct the defect ? Assume that the near point of the normal eye is 25 cm.
Solution:
(i) The near point N of hypermetropic eye is farther away from the normal near point N.

(ii) In a hypermetropic eye, the image of nearby object lying at normal near point N (at 25 cm) is formed behind the retina.

(iii) Correction of hypermetropia : The convex lens forms a virtual image of the object (lying at normal near point N) at the near point N’ of this eye.

The object placed at 25 cm from the correcting lens must produce a virtual image at 1 m or 100 cm.
Therefore, u = – 25 cm, ν = 100 cm

The positive sign shows that it is a convex lens.

Question 8
Why is a normal eye not able to see clearly the objects placed closer than 25 cm ?
Answer:
At distance less than 25 cm, the ciliary muscles cannot bulge the eye lens any more, the object cannot be focused on the retina and it appears blurred to the eye, as shown in the given figure.

Question 9
What happens to the image distance in the eye when we increase the distance of an object from the eye ?
Answer:
The eye lens of a normal eye forms the images of objects at various distances on the same retina. Therefore, the image distance in the eye remains the same.

Question 10
Why do stars twinkle ?
Answer:
Stars appear to twinkle due to atmospheric refraction. The light of star after the entry of light in earth’s atmosphere undergoes refraction continuously till it reaches the surface of the earth. Stars are far away. So, they are the point source of light. As the path of light coming from stars keep changing, thus the apparent position of stars keep changing and amount of light from stars entering the eye keeps twinkling. Due to which a star sometimes appear bright and sometimes dim, which is the effect of twinkling.

Question 11
Explain why the planets do not twinkle ?
Answer:
The planets are much nearer to the earth than stars and because of this they can be considered as large source of light. If a planet is considered to be a collection of a very large number of point sources of light, then the average value of change in the amount of light entering the eye from all point size light sources is zero. Due to this the effect of twinkling is nullified.

Question 12
Why does the sun appear reddish early in the morning ?
Answer:
The light coming from the sun passes through various denser layers of air in the earth’s atmosphere before reaching our eyes near the horizon. Most of the part of blue light and light of small wavelength gets scattered by dust particles near the horizon. So, the light reaching our eyes is of large wavelength. Due to this the sun appears reddish at the time of sunrise and sunset.

Question 13
Why does the sky appear dark instead of blue to an astronaut ?
Answer:
As an astronaut moves away from the atmosphere of earth, the atmosphere becomes thin. Due to the absence of molecules (or dust particles) in air, the scattering of light does not take place. Thus, sky appears dark in the absence of scattering.

NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World

Functioning of a lens in human eye, defects of vision and their corrections, applications of spherical mirrors and lenses. Refraction of light through a prism, dispersion of light, scattering of light, applications in daily life.

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Science
Chapter	Chapter 11
Chapter Name	Human Eye and Colourful World
Number of Questions Solved	17
Category	NCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Page 190

Question 1.
What is meant by power of accommodation of the eye?
Answer:
The power Of accommodation of the eye is the ability of the eye to observe the distinct objects clearly which are situated at a large distance from the eye. The ciliary muscles are responsible to change the focal length Of the eye lens. The value of the power of accommodation Of the normal human eye is (d = 25 cm) = 100/f = 100/d = 100/25 = 4 dioptres. The value of power of accommodation Of human eye is about 4D

Question 2.
A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?
Answer:
The far point for myopic eye is 1.2m.

More Resources for CBSE Class 10

Question 3.
What is the far point and near point of the human eye with normal vision ?
Answer:
For human eye with normal vision, far point is at infinity and near point is at 25 cm from the eye.
Download NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World PDF

Question 4.
A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from ? How can it be corrected ?
Answer:
As the child has difficulty in reading the blackboard, he is suffering from myopia or short sightedness. To correct this defect, he has to use spectacles with concave lens of suitable focal length.

Page 197 – 198
Question 1.
The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to
(a) presbyopia
(b) accommodation
(c) near-sightedness
(d) far-sightedness
Answer:
(b) Human eye can change the focal length of the eye lens to see the objects situated at various distances from the eye. This is possible due to the power of accommodation of the eye lens.

Question 2.
The human eye forms the image of an object at its
(a) cornea (b) iris (c) pupil (d) retina
Answer:
(d) The human eye forms the image of an object at its retina.

Question 3.
The least distance of distinct vision for a young adult with normal vision is about
(a) 25 m
(b) 2.5 cm
(c) 25 cm
(d) 2.5 m
Answer:
(c) The least distance of distinct vision is the minimum distance of an object to see clear and distinct image. It is 25 cm for a young adult with normal visions.

Question 4.
The change in focal length of an eye lens is caused by the action of the
(a) pupil
(b) retina
(c) ciliary muscles
(d) iris
Answer:
(c) The relaxation or contraction of ciliary muscles changes the curvature of the eye lens. The change in curvature of the eye lens changes the focal length of the eyes. Hence, the change in focal length of an eye lens is caused by the action of ciliary muscles.

Question 5.
A person needs a lens of power – 5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?
Answer:

Question 6.
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Answer:

Question 7.
Make a diagram to show how hypermetropia is corrected. The near point of a hypermetropic eye ¡s 1 m. What ¡s the power of a lens required to correct this defect? Assume that near point of the normal eye is 25 cm.

Question 10.
Why do stars twinkle?
Answer: The stars twinkle at night, because the star light reaching Our eyes increases and decreases continuously due to atmospheric refraction. When star light reaching our eyes increases, the star looks bright and when the star light reaching our eyes decreases, it appears dim.

Question 11.
Explain why the planets do not twinkle ?
Answer:
Planets being close to earth appear larger in size. A planet can be Considered as a collection of large number of small sized objects. Twinkling effect Of these objects cancel each other. so, planets do not appear to twinkle.

Question 12.
Why does the sun appear reddish early in the morning?
Answer: At sunrise, the sun looks almost reddish because only red colour which is least scattered is received by our eye and appears to come from sun. Hence the appearance Of sun at sunrise, near the horizon looks almost reddish.

Question 13.
Why does the sky appear dark of blue to an astronaut?
Answer:
At such huge heights due to absence of atmosphere, no scattering of the light takes place. Therefore sky appears dark.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
The human eye forms the image of an object at its [NCERT]
(a) cornea
(b) iris
(c) pupil
(d) retina
Answer:
(d) Retina is the light sensitive surface of eye on which the image is formed.

Question 2.
The human eye can focus objects at different distances by adjusting the focal length of eye lens. This is due to [NCERT]
(a) presbyopia
(b) accommodation
(c) nearsightedness
(d) farsightednes
Answer:
(b) Accommodation is the ability of eye lens to focus both near and distant objects by adjusting its focal length.

Question 3.
The change in focal length of eye lens is caused by action of [NCERT]
(a) pupil
(b) retina
(c) ciliary muscles
(d) iris
Answer:
(c) Ciliary muscles contract and extend in order to change the lens shape for focussing image ayretina.

Question 4.
The least distance of distinct vision for a young adult with normal vision is about [NCERT]
(a) 25 m
(b) 2.5 cm
(c) 25 cm
(d) 2.5 m
Answer:
(c) The minimum distance at which an object can be seen most distinctly without any strain is 25 cm.

Question 5.
At noon the Sun appears white as [NCERT Exemplar]
(a) light is least scattered
(b) all the colours of the white light are scattered away
(c) blue colour is scattered the most
(d) red colour is scattered the most
Answer:
(a) At noon, the Sun appears white because the light from the Sun is directly over head and travel relatively shorter distance. The Sun appears white as only a little of the blue and violet colours are scattered.

Question 6.
A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power [NCERT Exemplar]
(a) +0.5 D
(b) -0.5 D
(c) +0.2 D
(d) -0.2 D
If a person cannot see distinctly, objects kept beyond 21 m, then he is suffering from myopia.
Answer:
(b) As the person has the eye defect, myopia, therefore a concave lens has to be used whose focal length will be f = -2 m (using sign convention). Thus,
Power, P = 1/f [where, f is focal length in metre.]
= 1/-2 = -0.5D .

Question 7.
Which of the following phenomena of light are involved in the formation of a rainbow? [NCERT Exemplar]
(a) Reflection, refraction and dispersion
(b) Refraction, dispersion and total internal reflection
(c) Refraction, dispersion and internal reflection
(d) Dispersion, scattering and total internal reflection
Answer:
(c) A rainbow is caused by dispersion, refraction and internal reflection of sunlight by tiny water droplets, present in the atmosphere and always formed in a direction opposite to that of the Sun. The water droplets act like small prisms. They refract and disperse the incident sunlight, then reflect it internally and finally refract it again when it comes out of the raindrop.

Question 8.
A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident on the prism as shown in figure. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky? [NCERT Exemplar]

(a) Only (i)
(b) Only (ii)
(c) Only (iii)
(d) Only (iv)
Answer:
(b) In (ii) case, after dispersion, the third colour from the top corresponds to colour of the sky, i.e. blue.

Question 9.
A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his text book. Which of the following statements is correct?
(a) The near point of his eyes has receded away
(b) The near point of his eyes has come closer to him
(c) The far point of his eyes has come closer to him
(d) The far point of his eyes has receded away
Hypermetropia may have blurred vision to a person when looking at an object close to them and clearer 1 vision while looking at an object at the distance.
Answer:
(a) The student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his text book because he is suffering from hypermetropia or far sightedness. He can see distant objects clearly but cannot see nearby objects distinctly.

Question 10.
In the following diagram, the path of a ray of light passing through a glass prism is shown below.

In this diagram, the angle of incidence, the angle of emergence and the angle of deviation respectively, are [CBSE2014]
(a) X, R and T
(b) Y, Q and T
(c) X, Q and P
(d) Y, Q and P
Answer:
(d) Angle of incidence is the angle made by the incident ray with the normal to the first surface of prism, which is shown by angle Y. Angle of emergence is the angle made by the emergent ray with the normal to the surface when it comes out from the prism after refraction, which is shown by angle Q. Angle of deviation is the angle between the incident ray and the emergent ray, which is shown by angle P.

NCERT Solutions for Class 10 Science Chapter 11 Human Eye and Colourful World (Hindi Medium)

Class 10 Science Human Eye and Colourful World Mind Map

Human Eye

The organ which gives us the sense of light or enables us to see. It interprets the shapes, colours and dimensions of the

Parts of the Human Eye
Retina: It is a light sensitive screen on which image is formed.
It contains rods sensitive to intensity of light and cones sensitive to colour.
Cornea: Thin membrane acts like a lens which allow light to enter the eye.
Sclera: Outer part of the eye, protects interior of the eye.
Eye Lens: Convex lens made of transparent, crystalline and flexible jelly like material.
Refractive index of eye lens is 1.437
Ciliary Muscles: Modify the shape of eye lens.
Pupil: Hole in the middle of iris through which light enters.
Iris: Controls the amount of light entering the eye by changing the size of pupil.
Optical Nerve: Nerves take the image to the brain in the form of electrical signals.

Defects of Human Eye
Myopia or Short Sightedness: can see nearby objects but cannot see far off objects distinctly. Corrected by using a concave lens.
Hypermetropia or Long Sightedness: can see far off objects clearly but cannot see nearby objects clearly. Corrected by convex lens
Presbyopia: It is due to lessening of the flexibility of the crystalline lens and weakening of ciliary muscles. Corrected by using bifocal lenses.
Astigmatism: Refractive problem responsible for blurry vision. Corrected by using cylindrical lenses.
Cataract: It is a clouding of the lens in the eye. Corrected using cataract surgery

Power of Accommodation
The ability of the eye lens to adjust its focal length so as to see the objects clearly located anywhere. Near point of the human eye is 25 cm and far point of the human eye is infinity.

Object	Ciliary muscles	Suspensory ligaments	Muscle tension on lens	Lens shape
Near	Contract	Slackened	Low	Thick
Distant	Relax	Stretched	High	Thin

Persistence of Vision
Image of any object seen persists on the retina for 1/16 second even after the removal of the object. This property is used in cinematography.

Reason for Hypermetropia

Increase in focal length of eye lens
Shortening of eye-ball

Reason for Myopia

Excessive curvature of cornea
Elongation of eye-ball

Refraction
Bending of light when it passes obliquely from one medium to another medium

Dispersion
Splitting of white light into its component colours – VIBGYOR.
Red colour deviates least and violet deviates most

Cause of Dispersion
Refractive index of material for different wavelengths is different.
µ ∝\(\frac{1}{\lambda}\) µ_v > µ_r

Spectrum
Band of seven component colours VIBGYOR on a white screen

Rainbow
Seven colours band of sunlight in the form of bow in the sky. It is formed due to reflection, refraction and dispersion of sunlight by tiny water droplets. To observe rainbow, observer should stand with its back towards sun.

Colour
The sensation received by the eye (rod cells of the eye) due to light coming from an object.

Primary Rainbow

Two refraction and one total internal reflection
Subtends an angle of 42° at the eye of the observer
Innermost arc is violet and outermost is red
More bright

Secondary Rainbow

Two refraction and two total internal reflection
Subtends an angle of 52.5° at the eye
Innermost arc is red and outermost is violet
Less bright in comparison to primary rainbow

Atmospheric Refraction
Phenomena due to Refraction of light by atmosphere

- Twinkling of stars
- Stars seen higher than they actually are
- Advance sunrise and delayed sunset
- Flattering of the sun at morning and evening

Scatttering of Light

Rayleigh scattering Intensity of scattered light ∝ 1/λ⁴
Tyndall effect The smoke particles become visible
The reddening of the sun at sunrise and sunset
Blue colour of sky
The sky looks dark in absence of atmosphere
Danger signals are of red coloured

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NCERT Solutions for Class 10 Science All Chapters

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

March 6, 2026

NCERT Solutions For Class 10 Science Chapter 14 Sources Of Energy: Candidates who are searching for NCERT Solutions For Class 10 Science Chapter 14 Sources Of Energy can refer to this article. Sources of energy class 10 NCERT solutions pdf were solved by best physics faculty in India to provide strong command over the Physics subject.

Solving cbse class 10 physics sources of energy questions and answers will not only help candidates in making a good grade in board exams but also helps in cracking the competitive exam such as JEE, JEE Advanced, NEET, JIPMER etc., NCERT Solutions for sources of energy class 10 questions and answers were solved keeping various parameters in mind such as marking scheme, step marks, etc.,

So the candidates who wish to bag a decent score in the unit of sources of energy class 10 Science can scroll down to find out the NCERT Solutions For Class 10 Science Chapter 14.

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

Before getting into the details of Sources Of Energy Class 10 NCERT Solutions, let us look at the topics and subtopics under class 10 science chapter 14 notes:

Sources Of Energy
What Is A Good Source Of Energy?
Conventional Sources Of Energy
Alternative Or Non-Conventional Sources Of Energy
Environmental Consequences
How Long Will An Energy Source Last Us?

Free download NCERT Solutions for Class 10 Science Chapter 14 Sources Of Energy PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 14 Intext Questions

Page Number: 243

Question 1
What is a good source of energy?
Answer:
A good source of energy is one that

does a large amount of work per unit volume or mass
can be easily accessible
is easy to store and transport, and
is economical.

Question 2
What is a good fuel ?
OR
Write any three characteristics of a good fuel. [AICBSE 2015]
Answer:
A good fuel is one which has the following properties :

It should be fairly cheap.
It should be easily available.
Its ignition temperature should be well above normal temperature.
It should be conveniently handled and transported.
It should not produce any poisonous material during burning.
Its combustion rate should be steady and controllable.
It should not leave any residue or ash after burning.
A good fuel should have high calorific value so that higher amount of heat may be obtained by burning a little fuel.

Question 3
If you could use any source of energy for heating your food, which one should you use and why ?
Answer:
I would prefer to use cooking gas like LPG. It fulfils many of the criteria of a good fuel like its ignition temperature, good calorific value and non-polluting characteristics.

Page Number: 248

Question 1
What are the disadvantages of fossil fuels ?
Answer:
(i) The burning of fossil fuels produces large amount of carbon dioxide that causes increased greenhouse effect.
(ii) The burning of fossil fuels (such as coal) produces smoke which pollutes the air.
(iii) The burning of fossil fuels produces acidic gases such as sulphur dioxide and nitrogen oxide. These acidic gases cause acid rain that affects our water and soil resources.
(iv) Fossil fuels cannot be replenished in short time because it takes millions of years to form them.

Question 2
Why are we looking at alternate sources of energy ?
Answer:
We are looking at alternate sources of energy because of the following reasons.

The fossil fuels and nuclear fuels on the earth are limited which may not last for long.
The undesirable effects of pollution, both from the burning of fossil fuels and from the radioactive nuclear wastes of nuclear power plants are creating threat to our environment.

Question 3
How has the traditional use of wind and water energy been modified for convenience ?
Answer:
(i) Wind mill farms are constructed to produce electricity.
(ii) The traditional use of energy of flowing water has been modified by establishing hydro-power plants. At hydro-power plants, the energy of falling water or flowing water is tapped by using a water turbine and then made to drive generators.

Page Number: 253

Question 1
What kind of mirror-concave, convex or plane – would be the best suited for use in a solar cooker ? Why ?
Answer:
A concave mirror would be best suited in a solar cooker because it focuses the sunlight in a very small area of the solar cooker and a high temperature is produced in it which is sufficient to cook the food.

Question 2
What are the limitations of the energy that can be obtained from the oceans?
Answer:
The energy from the oceans can be obtained mainly in three forms. These are
(i) tidal energy
(ii) wave energy and
(iii) ocean thermal energy

Limitations of Tidal Energy :
(i) There are very few sites around the world which are suitable for building tidal dams.
(ii) The rise and fall of sea-water during high and low tides is not enough to generate electricity on a large scale.
Limitations of wave energy : The movement of ocean waves is associated with kinetic energy. Such sites in the world are limited where the waves strike the shore lines with sufficient power.
Limitations of ocean thermal energy : NCERT Solutions for Class 10 Science Chapter 14 Sources of EnergyTo convert ocean thermal energy into electricity, a temperature difference of 20°C (or more) between the surface water of ocean and deeper water is needed for operating OTEC power plants. This involves high cost.

Question 3
What is geothermal energy ?
Answer:
Energy stored as heat in certain regions of the earth (called hot spots) is called geothermal energy. Hot spots are the locations below earth’s crust where upward moving magma gets collected due to geological changes. When underground water comes in contact with the hot spots, steam is generated. This steam is utilised to generate electricity using pipes and turbines. Sometimes hot water from the hot spot finds outlet at the surface. Such outlets are called hot springs.

Question 4
What are the advantages of nuclear energy ?
Answer:
The advantages of nuclear energy are that :

It produces a large amount of useful energy from a very small amount of a nuclear fuel (like uranium-235).
Once the nuclear fuel (like uranium-235) is loaded into the reactor, the nuclear power plant can go on producing electricity for two to three years at a stretch. There is no need for putting in nuclear fuel again and again.
It does not produce gases like carbon dioxide which contributes to greenhouse effect or sulphur dioxide which causes acid rain.

Page Number: 253

Question 1
Can any source of energy be pollution free ? Why or why not ?
Answer:
No source of energy can be pollution free because even if it is clean, its assembly could have caused some environmental damage.

Question 2
Hydrogen has been used as rocket fuel. Would you consider it a cleaner fuel than CNG ? Why or why not ?
Answer:
Hydrogen is cleaner fuel than CNG. This is because the burning of hydrogen produces only water, which is totally harmless. On the other hand, burning of CNG produces carbon dioxide gas and water. The carbon dioxide can produce greenhouse effect in the atmosphere and lead to the excessive heating of the environment in long run.

Page Number: 243

Question 1
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Answer:
(i) Energy derived from biomass is a renewable source of energy because waste products are continuously produced. Plants and trees are also grown at reasonable intervals.
(ii) The energy derived from flowing water, wind, sun and ocean are renewable sources because these sources can be harnessed into energy so long as the present solar system exists.

Question 2
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Answer:
Fossil fuels like coal and petroleum are exhaustible sources of energy. The estimated reserves of these fuels are said to last us for about another 200 years, while it takes millions of years for these to be formed.

NCERT Solutions for Class 10 Science Chapter 14 Textbook Chapter End Questions

Question 1
A solar water heater cannot be used to get hot water on
(a) a sunny day
(b) a cloudy day
(c) a hot day
(d) a windy day
Answer:
(b) A cloudy day.

Question 2
Which of the following is not an example of a biomass energy source ?
(a) Wood
(b) Gobar gas
(c) Nuclear energy
(d) Coal
Answer:
(c) Nuclear energy.

Question 3
Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the sun’s energy ?
(a) Geothermal energy
(b) Wind energy
(c) Nuclear energy
(d) Biomass
Answer:
(a) Geothermal energy.

Question 4
Compare and contrast fossil fuels and the sun as direct sources of energy Ans
Answer:

Fossil fuels	Sun
(i) Non-renewable source of energy.	(i) Renewable source of energy.
(ii) Cause a lot of air pollution.	(ii) Pollution-free, doesn’t cause any pollution.
(iii) They will exhaust in future.	(iii) It is a non-exhaustible source.
(iv) Energy can be tapped throughout the year.	(iv) Energy cannot be tapped during night and cloudy and rainy days.

Question 5
Compare and contrast biomass and hydro-electricity as sources of energy. Ans.
Answer:

Biomass	Hydroelectricity
(i) Renewable source of energy.	(i) Renewable source of energy.
(ii) Biomass plants can be installed at any place to produce biomass as energy source.	(ii) Plants can be installed only at the places where dams can be constructed.
(iii) To collect waste materials is a tough and costly process.	(iii) Once the plants start to work, it is not difficult to collect water.

Question 6
What are the limitations of extracting energy from
(a) the wind ?
(b) waves ?
(c) tides ?
Answer:
(a) Limitations of wind energy
(i) Wind energy farms cannot be established everywhere. The wind energy farms can be established only at those places, where wind blows for most part of the year.
(ii) The wind required for generating electricity should be strong and steady to maintain the desired level of generation. The minimum wind speed necessary for satisfactory working of the wind generator is about 15 km/h. This is not always so.
(iii) The wind energy farms require a large area of land.
(iv) The setting up of wind energy farms is very expensive.

(b) Limitations of wave energy : The harnessing of sea-waves energy would be a viable proposition only at those places where sea-waves are very strong. This has constraints of time and location.

(c) Limitations of tidal energy :
(i) There are very few sites around the world which are suitable for building tidal dams.
(ii) The rise and fall of sea-water during high and low tides is not enough to generate electricity on a large scale.

Question 7
On what basis would you classify energy sources as
(a) renewable and non-renewable ?
(b) exhaustible and inexhaustible ?
Are the options given in (a) and (b) the same ?
Answer:
(a) Renewable sources : The sources of energy which are being produced continuously in nature and are inexhaustible, are called renewable sources of energy. The energy derived from flowing water, wind, tides, ocean waves, or wood are examples of energy from such sources.
Non-renewable sources : These sources are produced over million of years under special conditions. Once consumed, these are not replaceable for a very long time. Fossil fuels like coal, petroleum and natural gas are non-renewable sources.
(b) Exhaustible sources are non-renewable sources, while inexhaustible sources are renewable sources.
Yes, the options given in (a) and (b) are the same.

Question 8
What are qualities of an ideal source of energy ?
Answer:
An ideal source of energy

Must give an adequate amount of net energy.
Must be convenient to use so as to give energy at a steady rate.
Must be easy to store and transport.

Question 9
What are the advantages and disadvantages of using a solar cooker ? Are there places where solar cookers would have limited utility ?
Answer:
Advantages of using solar cooker :

The use of solar cooker for cooking food saves precious fuels like coal, kerosene and LPG.
The use of solar cooker does not produce smoke due to which it does not pollute air.
When food is cooked in solar cooker, its nutrients do not get destroyed. This is because in a solar cooker, food is cooked at a comparatively lower temperature.
In a solar cooker, up to four food items can be cooked at the same time.

Disadvantages of using solar cooker :

The solar cooker cannot be used to cook food during night because sunshine is not available at that time.
If the day sky is covered with clouds, even then solar cooker cannot be used to cook food.
The direction of reflector of solar cooker has to be changed from time-to-time to keep it facing the sun.
Sources of Energy
The box-type solar cooker cannot be used for baking (making chappattis, etc.) or for frying.
The places that receive rain most of the year or where the sky remains cloudy, the solar cooker has limited utility.

Question 10
What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption ?
Answer:
Some of the environmental consequences of the increasing demand for energy are the following :

The combustion of fossil fuels is producing acid rain and damaging plants (crops), soil and aquatic life.
The burning of fossil fuels is increasing the amount of greenhouse gas carbon-dioxide in the atmosphere. It has also affected the rainfall.
The cutting down of trees from the forest for obtaining fire-wood is causing soil erosion and destroying wild life.
The construction of hydro-power plants is disturbing ecological balance.
Nuclear power plants are increasing radioactivity in the environment.

The following steps can be taken to reduce energy consumption :

Switch off lights, fans, TV. and other such electrical appliances when not needed, to save electricity.
Use energy efficient electrical appliances to save electricity. This can be done by using compact fluorescent lamps (CFL) and tube lights in place of conventional filament- type electric bulbs.
Good quality stoves should be used to burn fuels like kerosene and LPG so as to obtain maximum heat.
Pressure cookers should be used for cooking food to save fuel.
Solar cookers should be used to cook food whenever possible and solar water heaters should be used to get hot water.
The use of biogas as fuel should be encouraged in rural areas.
Bicycles should be used for short distances to save fuel like petrol which is used in cars, scooters and motorcycles.

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy

Sources of energy : Different forms of energy, conventional and non-conventional sources
of energy: Fossil fuels, solar energy; biogas; wind, water and tidal energy; Nuclear energy, Renewable versus non-renewable sources of energy.

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Science
Chapter	Chapter 14
Chapter Name	Sources of Energy
Number of Questions Solved	24
Category	NCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Question 1
What is a good source of energy?
Solution:
A good source of energy would be one,
i) Which would do a large amount of work per unit volume or mass.
ii) Be easily accessible.
iii) Be easy to store and transport, and
iv) Perhaps most importantly, be economical.

Question 2
What is a good fuel?
Solution:
A good fuel would be one,
i) Which is easily available.
ii) It should not produce too much of smoke.
iii) On burning should release less amount of heat.

More Resources for CBSE Class 10

Question 3
If you could use any source of energy for heating your food, which one would you use and why?
Solution:
Solar energy can be used for heating food because it is easily available, it will not produce smoke and it will not release any amount of heat.

Download NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy PDF

Question 4
What are the disadvantages of fossil fuels?
Solution:
Fossil fuels are non-renewable. Burning of coal or petroleum products causes the air pollution. The oxides of carbon, nitrogen and sulphur that are released on burning fossil fuels are acid oxides. These lead to acid rain, which affects water and soil resources.

Question 5
Why are we looking at alternate sources of energy?
Solution:
The fossil fuels are non-renewable sources of energy. So we need to conserve them. If we were to continue consuming these sources at such alarming rates, we would soon run out of energy. In order to avoid this, alternate sources of energy were explored.

Question 6
How has the traditional use of wind and water energy been modified for our convenience?
Solution:
The wind possesses kinetic energy. This energy was harnessed by windmills in the past to do mechanical work. Today, wind energy is also used to generate electricity.
Another traditional source of energy was the kinetic energy of flowing water or the potential energy of water at a height. Hydropower plants convert the potential energy of falling water into electricity.

Question 7
What kind of mirror – concave, convex or plane – would be best suited for use in a solar cooker? Why?
Solution:
Plane mirror would be best suited for use in a solar cooker. A plane mirror is used as a reflector. The reflector is used to increase the area over which the solar energy is collected so that more and more heat rays of the sun may enter the solar cooker.

Question 8
What are the limitations of the energy that can be obtained from the oceans?
Solution:
The energy from the oceans can be obtained mainly in three forms,
a) Tidal energy
b) Ocean waves energy
c) Ocean thermal energy
The energy potential from sea is quite large, but efficient commercial exploitation is difficult.

Question 9
What is geothermal energy?
Solution:
‘Geo’ means ‘earth’ and ‘thermal’ means ‘heat’. Thus the geothermal energy is the heat energy from the hot rock present inside the earth. This heat can be used as a source of energy to produce electricity.

Question 10
What are the advantages of nuclear energy?
Solution:
The advantages of nuclear energy is as follows,
(a) It generates electricity.
(b) Disease like cancer can be treated.
(c) It helps for the improvement in the agriculture and industry.

Question 11
Can any source of energy be pollution-free? Why or why not?
Solution:
Yes, Solar energy does not cause any pollution. Solar cells make use of the ‘everlasting solar energy’ and their use does not produce any environmental pollution.

Question 12
Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Solution:
Yes, hydrogen is a cleaner fuel than CNG because of its very high colorific value, hydrogen is an extremely good fuel.

Question 13
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Solution:
Hydro Energy and Solar Energy
Hydro energy or water energy is renewable source of electric energy, which will never get exhausted, since water is available in plenty.
Solar energy is also known as light energy, which is obtained from the sun and it will never get exhausted.

Question 14
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Solution:
Coal and petroleum are the two energy sources that are considered to be exhaustible. They are non-renewable sources of energy and are present in a limited amount in the earth. Once exhausted, they will not be available to us again.

Question 15
A solar water heater can be used to get hot water on
(a) a sunny day.
(b) a cloudy day.
(c) a hot day.
(d) a windy day.
Solution:
(a) a sunny day.

Question 16
Which of the following is not an example of a bio-mass energy source?
(a) wood
(b) gobar-gas
(c) nuclear energy
(d) coal.
Solution:
(c) nuclear energy.

Question 17
Most of the sources of energy we use represent stored solar energy.
Which of the following is not ultimately derived from the Sun’s energy?
(a) geothermal energy
(b) wind energy
(c) nuclear energy
(d) bio-mass.
Solution:
(c) nuclear energy.

Question 18
Compare and contrast fossil fuels and the Sun as direct sources of energy.
Solution:
Fossil fuels are non-renewable sources of energy. These non-renewable sources of energy (like coal, petroleum, natural gas) are present in a limited amount in the earth. Once exhausted, they will not be available to us again.
The sun is the source of all energy. The sun is a renewable source of energy, provides us heat and light energy free of cost. The energy obtained from the sun is called solar energy. The energy coming from the sun contains heat rays, visible light, ultra-violet rays and some gamma rays.

Question 19
Compare and contrast bio-mass and hydro electricity as sources of energy.
Solution:
The waste material of living things and the dead parts of living things is called bio-mass. Bio-mass contains carbon compounds and it is the oldest source of heat energy for domestic purposes. The important examples of bio-mass being used as a fuel are wood, cattle dung and agriculture wastes like bagasse.
Hydropower plants convert the potential energy of falling water into electricity. Water energy is a renewable source of electric energy, which will never get exhausted. The construction of dams on rivers helps in controlling floods and in irrigation.

Question 20
What are the limitations of extracting energy from
(a) the wind?
(b) waves?
(c) Tides?
Solution:
a) There are many limitations in harnessing wind energy. Wind energy farms can be established only at those places where wind blows from the greater part of a year. The wind speed should also be higher than 15 Km/h to maintain the required speed of the turbine. There should be some back-up facilities to take care of the energy needs during a period when there is no wind.
b) The waves are generated by strong winds blowing across the sea. Wave energy would be a viable proposition only where waves are very strong.
c) Tidal energy is harnessed by constructing a dam across a narrow opening, the location where such dams can be built are limited.

Question 21
On what basis would you classify energy sources as
(a) renewable and non-renewable?
(b) exhaustible and inexhaustible?
Are the options given in (a) and (b) the same?
Solution:
The options given in (a) and (b) are the same.
Those sources of energy, which are being, produced continuously in nature and are inexhaustible are called renewable sources of energy.
Those sources of energy, which have accumulated in nature over a very, very long time and cannot be quickly replaced when exhausted are called non-renewable sources of energy.

Question 22
What are the qualities of an ideal source of energy?
Solution:
The important qualities of an ideal source of energy is
a) It should be a renewable source of energy.
b) It should be pollution-free.
c) It should be economical.
d) It should be easily accessible.

Question 23
What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Solution:
The advantages of a solar cooker
i) The use of solar cooker for cooking food saves fuel.
ii) The use of solar cooker does not produce smoke due to which the environment also does not get polluted.
iii) When food is cooked in a solar cooker, its nutrients do not get destroyed. This is because in a solar cooker, food is cooked at comparatively lower temperature.
iv) In a solar cooker, upto four food items can be cooked at the same time.
The disadvantages of a solar cooker
i) The box-type solar cooker cannot be used to make chappaties.
ii) The box-type solar cooker cannot be used for ‘frying’.
The limited utility of a solar cooker is
i)The solar cooker cannot be used to cook the food during nighttime.
ii) If the day-sky is covered with clouds, even then the solar cooker cannot be used to cook the food.
iii) The direction of reflector of solar cooker has to be changed from time to time to keep it facing the sun.

Question 24
What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Solution:
Exploiting any source of energy disturbs the environment in some way or the other. The source we would choose depends on factors such as the case of extracting energy from that source, the economics of extracting energy from the source, the efficiency of technology available and the environmental damage that will be caused by using that source.
We cannot depend on the fossil fuels for much longer, if we manage bio-mass by replacing the trees we cut down for fire-wood, we can be assured of a constant supply of energy at a particular rate. Renewable energy is available in our natural environment, in the form of some continuing or repetitive current of energy, or is stored in such large under ground reservoirs that the rate of depletion of reservoirs because of extraction of usable energy is practically negligible.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
Which of the following is a non-renewable source of energy? [NCERT Exemplar]
(a) Wood
(b) Sun
(c) Fossil fuel
(d) Wind
Answer:
(c) The fossil fuels are non-renewable sources of energy whereas wood, the Sun and wind are renewable sources of energy. Non-renewable sources of energy are those which are exhaustible and cannot be replaced, once they have been used. They are also known as conventional sources of energy.

Question 2.
Fuel used in thermal power plant is [NCERT Exemplar]
(a) water
(b) uranium
(c) bio-mass
(d) fossil fuels
Answer:
(d) The thermal power plant generates electric power from heat produced by burning fossil fuel, i.e. coal and petroleum. Everyday we burn a large amount of fossil fuels to heat up water to produce steam. The steam so produced runs turbines to generate electricity.

Question 3.
In a hydroelectric power plant more electrical power can be generated, if water falls from a greater height because [NCERT Exemplar]
(a) its temperature increases
(b) a large amount of potential energy is converted into kinetic energy
(c) the electricity content of water increases with height
(d) more water molecules dissociate into ions
Answer:
(b) In a hydroelectric power plant, more electrical power can be generated, if water falls from a greater height, because the rise in water level causes the increase in potential energy of water. Thus, when it flows from higher position more amount of kinetic energy is formed by the conversion of higher potential energy and this kinetic energy in the form of moving water can produce more electrical power.

Question 4.
The power generated in a windmill [NCERT Exemplar]
(a) is more in rainy season, since damp air would mean more air mass hitting blades
(b) depends on the height of the tower
(c) depends on wind velocity
(d) can be increased by planting tall trees close to the tower
Answer:
(c) Wind energy farms can be located only in vast open areas located in favourable wind conditions as the minimum velocity for a windmill to functions is 11-16 km/h and is called as cut in speed. Thus, the power generated in a windmill depends on wind velocity.

Question 5.
Choose the correct statement. [NCERT Exemplar]
(a) Sun can be taken as an inexhaustible source of energy
(b) There is infinite storage of fossil fuel inside the Earth
(c) Hydro and wind energy plants are non-polluting sources of energy
(d) Waste from a nuclear power plant can be easily disposed off
Answer:
(a) The Sun has been radiating an enormous amount of energy at the present rate for nearly 5 billion years and will continue radiating at that rate for about 5 billion years more, so the Sun can be taken as an inexhaustible source of energy.

Question 6.
Which part of the solar cooker is responsible for greenhouse effect? [NCERT Exemplar]
(a) Coating with black colour inside the box
(b) Mirror
(c) Glass sheet
(d) Outer cover of the solar cooker
Answer:
(c) Glass sheet present in the solar cooker easily passes the radiation into the solar cooker and the radiation gets absorbed and that reflected back by the black coating is of longer wavelength and cannot pass back out through the glass. Thus, glass sheet produces greenhouse effect in solar cooker.

Question 7.
Ocean thermal energy is due to [NCERT Exemplar]
(a) energy stored by waves in the ocean
(b) temperature difference at different levels in the ocean
(c) pressure difference at different levels in the ocean
(d) tides arising out in the ocean
Answer:
(b) The water at the surface of the sea or ocean is heated by the Sun, while the water in deeper sections is relatively cold. This difference in temperature between these layers ranges from 10-30 °C and is exploited to obtain energy. Thus, ocean thermal energy is due to temperature difference at different levels in the ocean.

Question 8.
The major problem in harnessing nuclear energy is how to [NCERT Exemplar]
(a) split nuclei
(b) sustain the reaction
(c) dispose off spent fuel safely
(d) convert nuclear energy into electrical energy
Answer:
(c) The major hazard of nuclear power generation is the storage and disposal of spent or used fuels. Improper nuclear waste storage and disposal result in environmental contamination as well as risk of accidental leakage of nuclear radiation. It happened in Chernobyl disaster 1986, Fukushima Nuclear disaster 2011 caused great damage to the living beings and habitats.

NCERT Solutions for Class 10 Science Chapter 14 Sources of Energy (Hindi Medium)

Class 10 Science Sources of Energy Mind Map

SOURCES OF ENERGY
(Plants, winds, water, coal, bio-gas, natural gas etc.)

It should not affect the environment. It should be eco-friendly.
Biogas is a mixture of methane (75%) CO₂, hydrogen and traces of hydrogen sulphide. Methane is an extremely good fuel

Environmential Consequences

Air pollution and acid rain
Green house effect
Damage to water bodies and to human life.

Types of Sources of Energy

Renewable Sources of Energy
Non- Renewable Sources of Energy

Renewable Sources of Energy
Which can be easily generated and whose supply is unlimited.

Hydro Power Plants
The potential energy of falling water is converted into electricity.

Limited Dams
Construction needs a large area
Eco-systems are destroyed
High lost of installation
About 20% of the power generated in India comes from hydro power plants

Wind Energy
When wind blows with a sufficient speed, it gets ability to do some work
It doesn’t pollute the air like power plants that rely on combustion of fossil fuels

Wind mill
It is a device which is used to convert wind energy into electrical energy. More than 25% of the electricity needs are generated through a vast network of wind mills.

Wind farm and power plants
It is basically used to generate electricity on a commercial basis, (large scale)
Wind power plants needs high maintenance and high wind speeds
Wind farms are noisy and may spoil the view for people living near them

Biomass
It means any organic matter from which we get energy on a renewable basis

Solar Energy
The energy coming with the rays of the sun. The ultimate source of energy

Solar Cooker
It is a device that uses solar energy to cook food

Solar Panel
It is a combination of large number of solar cells to draw high voltage for commercial purposes

Solar Cells
It is a device which converts solar energy into electric energy
Solar cells can be used in many small appliances like calculators and spacecrafts

Energy from the Sea
Form of energy obtained from the ocean in the form of tidal waves; wind blowing etc.

Tidal energy
It is a form of energy which is obtained from the ocean in the form of tidal waves

Wave energy
It is a another type of ocean based energy source that uses the power of waves to generate electricity

Ocean thermal energy (OTE)
This energy is obtained from using the temperature difference between deep cold ocean water ane warm surface water

Geothermal energy
It is the energy which is stored in the form of heat inside the earth

Characteristics of good sources of energy

Easy storing and transportation
Easy access
Large amount of work per unit volume or mass
Economical

Non-Renewable Sources of Energy
Which cannot be generated easily and whose supply is limited

Advantages

High in energy
Profitable
Easy to use
Cost effective

Disadvantages

Time consuming to extract
Dangerous for humans
Contribution to acid rain
Not viable for future generations

Fossil Fuels
These are hydrocarbons based natural resources that were formed 300 millions years ago.

Thermal Power Plant
Fuel is burnt to produce heat energy which is converted into electrical energy

Advantages

Smaller space is required as compared to hydro power plant
Running costs are less compared to gas plants or diesel

Major Hazards
Causes Air Pollution Green House Effect and Acid Rain

Nuclear Energy
Energy released during nuclear reactions

Types of Nuclear Energy
Nuclear Fission
It is a process in which a heavy nucleus splits up into two lighter nuclei
→ ₉₂U²³⁵ + ₀n¹
₅₆Ba¹⁴¹ + ₃₆Kr⁹² + 3₀n¹ + energy

This principle is used in atom bomb

Moderator
Slow down fast moving neutrons e.g.: heavy water, graphite

Coolant
Remove heat e.g.: cold water, liquid oxygen

Control rods
Absorb neutrons e.g.: boron, cadmium

Nuclear Fusion
It is a process in which two lighter nuclei combine together to form a heavier nucleus
₁H² + ₁H² + ₁H² → ₂He⁴ + ₁H¹ + ₀n¹ + 21.6 Mev

This principle is used in hydrogen bomb

Major Hazards

Storage of spent fuels.
Disposal of spent fuels.
High cost of Installation
Limited availability of fuel.

Now that you are provided all the necessary information regarding NCERT Solutions For Class 10 Science Chapter 14 Sources Of Energy and we hope this detailed article on sources of energy class 10 questions and answers are helpful. If you have any doubt regarding this article or cbse class 10 physics sources of energy questions and answers, drop your comments below and we will get back to you at the earliest.

NCERT Solutions for Class 10 Science All Chapters

NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination

March 6, 2026

NCERT Solutions For Class 10 Science Chapter 7 Control And Coordination: In this article, you will find out everything about NCERT Solutions For Class 10 Science Chapter 7 Control And Coordination. Candidates can find everything about control and coordination class 10 extra questions with answers in this article.

The answer to each and every question in class 10 science chapter 7 notes is provided along with complete, step-wise solutions for candidates better understanding. This will further help candidates in their home assignments and as well as practice sessions. Read on to find everything about Control and Coordination Class 10.

Free download NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination PDF in Hindi Medium as well as in English Medium for CBSE, Uttarakhand, Bihar, MP Board, Gujarat Board, and UP Board students, who are using NCERT Books based on updated CBSE Syllabus for the session 2019-20.

NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination

Before getting into the details of NCERT Solutions For Class 10 Science Chapter 7 Control And Coordination, let’s have an overview of topics and subtopics under control and coordination class 10 NCERT questions:

Control And Coordination
Animals – Nervous System
Coordination In Plants
Hormones In Animals

Control and Coordination Class 10

NCERT Solutions for Class 10 Science Chapter 7 Intext Questions

Page Number: 119

Question 1
What is the difference between a reflex action and walking?
Answer:

Reflex action	Walking
1. It is the action which is performed automatically.	1. It is a response to the information transmitted by nerve to muscles of the legs. In this case, thinking is involved.
2. It is controlled and coordinated by spinal cord.	2. Brain instructs and controls leg muscles to move.
3. It is an involuntary action.	3. It is a voluntary action.

Question 2
What happens at the synapse between two neurons?
Answer:
The small empty space between two nerve cells is called synapse. At synapse, a chemical substance is produced at the end of axon of one nerve cell that reaches to the other nerve cell through the dendrite. Thus, information is transmitted from one nerve cell to other nerve cell by synapse.

Question 3
Which part of the brain maintains posture and equilibrium of the body ?
Answer:
Posture and equilibrium of the body are controlled by cerebellum.

Question 4
How do we detect the smell of an agarbatti (incense stick) ?
Answer:
The smell of agarbatti (incense stick) diffuses in the air. It is detected by olfactory receptors present in the nose. This information is sent to olfactory lobe by sensory nerves located in the forebrain. It responds to the information.

Question 5
What is the role of the brain in reflex action ?
Answer:
There is no role of brain in reflex action. These involuntary actions are controlled by the spinal cord which take place immediately without thinking of how to respond to the stimuli.

Page Number: 122

Question 1
What are plant hormones ?
Answer:
Plant hormones are also called phytohormones. Plant hormones are the chemical substances which help in controlling growth, flowering, height, development of plants and their response to the environment.

Different types of phytohormones are – auxins, gibberllins, cytokinins, abscisic acid and ethylene.

Question 2
How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light ?
Answer:

Movement of leaves of sensitive plant	Movement of a shoot towards light
1. It is a nastic movement which does not depend on the direction of stimulus applied.	1. It is a tropic movement which depends on the direction of stimulus applied.
2. The stimulus is touch.	2. The stimulus is light.
3. It is caused by the sudden loss of water from the swellings at the base of leaves.	3. It is caused by the unequal growth on the two sides of the shoot.
4. It is not a growth movement.	4. It is a growth movement.

Question 3

Give an example of a plant hormone that promotes growth.
Answer:
Auxin.

Question 4
How do auxins promote the growth of a tendril around a support ?
Answer:
When the tip of a tendril touches a support, then the auxins present in its tip move to that side of tip which is away from the support. Auxins promote growth. So, due to more auxins in it, the side of tendril away from the support grows faster (and becomes longer) than the side which is in contact with the support and makes the tendril twirl (or bend) around the support.

Question 5
Design an experiment to demonstrate hydrotropism.
Answer:
Take two glass troughs A and B and fill each one of them two-thirds with soil. In trough A plant a tiny seedling. In trough B plant a similar seedling and place a c/ay pot inside the soil. Water the soil in trough A daily and uniformly. Do not water the soil in trough B but put some water in the clay pot. Leave both the troughs for a few days.

Now, dig up the seedlings carefully from both the troughs without damaging their roots. We will find that the root of seedling in trough A is straight. On the other hand, the root of seedling in trough B is found to be bent to the right side i.e., towards the clay pot containing water.
In trough A, the root of the seedling gets water from both sides. But in trough B, the roots get water oozing out from the clay pot which is kept on the right side. Therefore, the root of seedling in trough B grows and bends towards the source of water to the right side. This experiment shows that the root of a plant grows towards water. In other words, the root of a plant is hydrotropism.

Page Number: 125

Question 1
How does chemical coordination take place in animals ?
Answer:
Chemical coordination in animals takes place through the hormones secreted by the endocrine glands. Coordination in animals takes place through hormone system as well as nervous system which is called endocrine system. Endocrine glands secrete animal hormones directly into the blood that reach to the specific cells. Special type of molecules are present on the surface of cells to detect these hormones. These cells act according to the information that a particular hormone carries.

Question 2
Why is the use of iodised salt advisable ?
Answer:
It is advised to use iodised salt because thyroid gland needs iodine to produce thyroxin hormone. Thyroxin hormone controls all the metabolic activities of our body like metabolism of carbohydrates, fats and protein etc. Due to the deficiency of thyroxin a disease called goitre is caused.

Question 3
How does our body respond when adrenaline is secreted into the blood ?
Answer:
The heart beat increases when adrenaline is secreted into the blood so that more oxygen is supplied to our muscles. The blood supply to the digestive system and skin decreases because the small arteries around the muscles of these organs contract. This turns the direction of blood towards our skeletal muscles. The breathing rate also increases due to the contractions of the diaphragm and rib muscles. All these responses enable us to face the situations of fear and anger.

Question 4
Why are some patients of diabetes treated by giving injections of insulin ?
Answer:
Insulin hormone regulates blood sugar levels. If this is not secreted in proper amounts, the sugar level in the blood rises. This causes many harmful effects.
To treat harmful effects of increased level of blood sugar, the diabetic patients are treated by giving injections of insulin.

NCERT Solutions for Class 10 Science Chapter 7 Textbook Chapter End Questions

Question 1
Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Answer:
(d) Cytokinin

Question 2
The gap between two neurons is called a
(a) dendrite
(b) synapse
(c) axon
(d) impulse
Answer:
(b) Synapse

Question 3
The brain is responsible for
(a) thinking
(b) regulating the heart beat
(c) balancing the body
(d) all of the above
Answer:
(b) All of the above

Question 4
What is the function of receptors in our body ? Think of situations where receptors do not work properly. What problems are likely to arise ? [AICBSE 2016]
Answer:
Receptors are specialised cells located in our sense organs like ear, nose, skin, tongue and eyes. The function of receptors is to detect information from the environment. For example, olfactory receptors detect smell. If receptors do not work properly, the information obtained from the environment will be delayed to reach the spinal cord or brain. In this situation, the response to the environmental stimulus will be delayed causing harm to the body. For example, if skin receptors are damaged, and one accidentally touches a hot object, then his/her hands might get burn as the damaged receptor cannot perceive the external stimuli of heat and pain.

Question 5
Draw the structure of a neuron and explain its function. [AICBSE 2017]
Answer:
Nerve cell or neuron is the functional unit of nervous system. A nerve cell has three parts-
(i) cell body
(ii) dendrite
(iii) axon

Function : The function of nerve cells is to carry information in the form of electrical signals which are called nerve impulses. Cells receive stimulus to send it to spinal cord and brain and carry the message from brain to the target organ.

Question 6
How does phototropism occur in plants ?
Answer:
The movement in any part of a plant due to light is called phototropism. The shoot of plant shows positive phototropism and roots show negative phototropism.
Phototropism in plants occurs due to the hormone auxin. When light falls on one side of a plant, the secretion of auxin hormone is more in the part away from the light. Hence, auxin causes growth in length of the cells in shady part. So, the plant appears to bend towards light.

Question 7
Which signals will get disrupted in case of a spinal cord injury ?
Answer:
(i) All the involuntary actions will get disturbed.
(ii) Reflex actions will be disturbed because reflexes are located in the spinal cord. Therefore, the quick responses required to safe guard the body will not take place.

Question 8
How does chemical coordination occur in plants ?
Answer:
Chemical coordination in plants takes place with the help of plant hormones. In most of the regions where division takes place (meristematic regions) stimuli cells secrete chemical compounds (hormone). These substances identify the information by stimulating the other nearby cells and communicating the information.

Question 9
What is the need for a system of control and coordination in an organism ?
Answer:
An organism needs control and coordination system for the following functions :
(i) To save the body of the organisms from the harmful changes in the environment.
(ii) To control the speed of voluntary and involuntary actions.
(iii) To have the capability to think and learn for responding to any stimuli.

Question 10
How are involuntary actions and reflex actions different from each other ?
Answer:

Involuntary actions	Reflex actions
1. Those actions which occur immediately without any thinking are called involuntary actions.	1. Reflex action is an immediate response to an event which does not require any processing by brain.
2. Involuntary actions are controlled by mid and hind brain. Example: Breathing, beating of heart, etc.	2. Reflex actions are controlled by spinal cord. Example: Sneezing, coughing, etc.

Question 11
Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Answer:

Nervous mechanism	Hormonal mechanism
It is a fast process.	It is a slow process.
Arteries and glands are affected.	It affects the target organ.
It transmits in electrochemical form.	It transmits in chemical form.
It does not control metabolism.	It controls metabolism.
Growth is not affected.	Growth is affected.

Question 12
What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs ?
Answer:

Movement in a sensitive (mimosa) plant	Movement in legs of a human
1. The leaves of a sensitive plant like mimosa are sensitive to touch.	1. Leg is in control of nerve muscles.
2. It is not controlled by any part of the plant.	2. It is controlled by brain and spinal cord.
3. In this, cells change their shape on changing the amount of water in them.	3. Amount of water has no effect on the movement of muscles.
changing the amount of water in them.	the movement of muscles.
4. The movement in a sensitive plant are nastic movement.	4. The movement in our leg is due to voluntary nervous system.

Control and Coordination Class 10 HOTS

Question 1.
What type of plant movement is seen in the diagram of coiling of tendril?

How do auxins promote the growth of a tendril around a support? Describe in brief. (CCE 2012)
Answer:
Thigmotropism or curvature movement that occurs in response to contact. Less auxin is present in the region of contact. The free side having more auxin shows more growth. This causes the tendril to coil over the support.

Question 2.
Identify and label the parts shown as A and B in the accompanying figure.

Answer:
Dorsal view of thyroid an parathyroid.
A – Thyroid,
B- Parathyroid.

Question 3.
What are the hormones involved in providing milk to the suckling infant ?
Answer:
1. Prolactin (Maternity Hormone). Production of milk.
2. Oxytocin Ejection of milk.

Question 4.
How does pancreas control glucose level of blood ?
Answer:
Pancreas produces two hormones

Insulin from P-cells of islet of Langerhans and
Glucagon from a- cells of islets of langerhans.

Insulin is produced when glucose level of blood rises. Insulin helps the cells to withdraw glucose from blood. It also converts glucose into glycogen in liver and muscles.

Question 5.
Glucagon is secreted when glucose level of blood falls. It mobilises reserve food like glycogen into glucose. What is pregnancy hormone ? Why is it known so ?
Answer:
Progesterone is called pregnancy hormone. It helps in maintaining pregnancy by non-formation of new ova, promoting thickening and secretory activity of uterine wall and attachment of embryo to the uterine wall.

Question 6.
What is dormin ?
Answer:
Dormin is the other name of plant hormone abscisic acid. The hormne induces dormancy in buds and seeds. So it has been called dormin.

Question 7.
(a)

Name the parts labelled A and B in the neuron drawn above.
Which part acquires the information in the neuron ?
Through which part does the information travel ?
In what form does this information travel ?
Where is the impulse converted into a chemical signal for onward transmission ?

(b) Name the hormone secreted by thyroid. What is the function ?
(c) Why is the use of iodised salt advisable ?
(CBSE A.I. 2008 Compt.)
Answer:
(a)

A-Dendrite, B-Axon
Dandrite.
Dandrite to cell body or cyton to axon.
Electrical impulse
In the region of synapse.

Impulse stimulates the release of chemical neurotransmitter from the surface of presynaptic knob or bouton of axon terminal. Neurotransmitter (e.g. acetylcholine) comes in contact with chemoreceptor sites of post-synaptic membrane of the next neuron and generates a fresh impulse.

(b) Thyroxine:
Function of Thyroxine. It controls

Basal metabolic rate
Metabalism of carbohydrates, fats and proteins
Consumption of energy in physical activity and body temperature
Development and differentiation.

(c) Iodised Salt: Salt is iodised to provide iodine to thyroid for synthesis of thyroxine which is iodine containing hormone.

Question 8.
(a) What are plant hormones ? Give one example each of a plant hormone that

promotes growth
inhibits growth.
promotes cell division
promotes the growth of a tendril around a support. (CCE 2011)

(b) Name the parts labelled A, B and C in the diagram given below. Write one function of each part. (CBSE A.I. 2008 Comptt. Delhi 2008 Comptt.)

Answer:
(a) Plant Hormones:
Phytohormones are chemical substances other than nutrients produced naturally in plants which regulate growth, development, differentiation and a number of physiological processes, e.g., auxin, gibberellins, abscisic acid, cytokinins.

Hormone That Promotes Growth. Auxin/Gibberellin.
Hormone That Inhibits Growth. Abscisic acid or ABA
Hormone That Promotes Cell Division. Cytokinin.
Hormone That Promotes Growth of a Tendril Around a Support. Auxin.

(b) A-Pons Function: Relay centre, pneumotaxic area of respiratory centre.
B-Medulla Function: Reflex centre, cardiac centre, respiratory centre.
C-Cerebellum Function: Maintains equilibrium and coordinates muscular activities

Control and Coordination Class 10 Value Based Questions

Question 1.
How do tendrils reach the support when they do not have any sensory structures.
Answer:
Tendrils do not have any sensory structures but still they are able to find their support just as we grope in the dark for finding the switch-board. Tendrils perform circumnutation from their apical regions. In this the terminal parts of tendrils move in all directions. Wherever they come in contact with a support, they stop performing cicumnutation. Instead, the contacted region shows little growth while the other side grows rapidly so that the tendril coils over the support.

Question 2.
Name the nervous system which controls the functioning of internal organs. How does this system work ?
Answer:
Autonomous or visceral nervous system. The system does not consult the will of the individual. It works on its own inputs. Autonomous nervous system consists of only motor nerve fibres that innervate all organs and glands of the body. Depending upon the input, autonomous nervous system stimulates, slows down or stops the activity of an organ. For its working, autonomous or visceral nervous system has two components, sympathetic and parasympathetic. Sympathetic nervous system originates from thoracico-lumbar region, forms two ganglionic chains which send out long nerve fibres to various organs. The sympathetic nerve fibres activate the organs by release of nor-adrenaline. Parasympathetic nervous system is called cranio-sacral as it originates from some cranial and sacral nerves. It has long preganglionic fibres and ganglia attached to organs that are innervated. Its post ganglionic fibres secrete acetylcholine into organs for moderating or reducing their activity.

Question 3.
Which system is working when you start sweating during exercise ? What is its function ?
Answer:
Reflex activity of the nervous system. Actually 90% of nervous activity is performed through reflexes. It is automatic, involuntary and spontaneous response to a stimulus without consulting the will of the individual. Exercise increases body temperature. This can be harmful. Reflex action stimulates the sweat glands for releasing their secretion. Part of the sweat evaporates and cools, down the body.

Question 4.
You can become moody by simply switching on night bulb daily. How can this happen ?
Answer:
Night bulb reduces the secretion of melatonin hormone. Melatonin controls our day-night or circadian rhythm, healthy digestive and immune system, sexual cycle and moods. A reduced secretion causes insomnia and mood changes besides affecting health of our digestive and immune system.

NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination

Control and co-ordination in animals and plants: Tropic movements in plants; Introduction to plant hormones; Control and co-ordination in animals, nervous system; voluntary, involuntary and reflex action; Chemical co-ordination: animal hormones.

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Science
Chapter	Chapter 7
Chapter Name	Control and Coordination
Number of Questions Solved	26
Category	NCERT Solutions

Formulae Handbook for Class 10 Maths and Science

Question 1
What is the function of receptors in our body?
Solution:
Receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell.

Question 2
Draw the structure of neuron and explain its function.
Solution:

The specialised tips of some nerve cells detect all information from our environment. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell. This information, acquired at the end of the dendritic tip of a nerve cell, sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. This is a general scheme of how nervous impulses travel in the body. A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland. It is thus no surprise that nervous tissue is made up of an organized network of nerve cells or neurons, and is specialised for conducting information via electrical impulses from one part of the body to another.

Question 3
How does phototropism occur in plants?
Solution:

Phototropism is a growth movement induced by a light stimulus. Growth towards a source of light is called positive phototropism, that away from the source is termed negative phototropism. The tips of shoots are usually positively, that of roots negatively phototropic.
Charles Darwin and his son Francis discovered (in 1880) that the phototropic stimulus is detected at the tip of the plant.
The Darwins used grass seedlings for some of their experiments. When grass seeds germinate, the primary leaf pierces the seed coverings and the soil while protected by the coleoptile, a hollow, cylindrical sheath that surrounds it. Once the seedling has grown above the surface, the coleoptile stops growing and the primary leaf pierces it.
The Darwins found that the tip of the coleoptile was necessary for phototropism but that the bending takes place in the region below the tip.
If they placed an opaque cover over the tip, phototropism failed to occur even though the rest of the coleoptile was illuminated from one side.
However, when they buried the plant in fine black sand so that only its tip was exposed, there was no interference with the tropism – the buried coleoptile bent in the direction of the light.
From these experiments, it seemed clear that

The stimulus (light) was detected at one location (the tip)
The response (bending) was carried out at another (the region of elongation).
This implied that the tip was, in some way, communicating with the cells of the region of elongation.

Question 4
How does chemical coordination occur in plants?
Solution:
It has been found that the growth of plants is regulated by certain chemical substances which are synthesized by the plants in very small amounts. These are known as plant hormones or phytohormones.

They are the organic substances which either promote or inhibit growth. A phytohormones can be defined as a chemical substances which are produced naturally in plants and are capable of translocation and regulating one or more physiological processes when present in low concentration. Main categories of plant hormones are:

Auxins
Gibberellins
Cytokinins
Ethylene
Abscisic acid

Auxins and Gibberellins stimulate cell elongations, cytokinins stimulate cell division ethylene promotes transverse or isodiametric growth and abscisic acid is a growth inhibitor.

Question 5
What is the need for a system of control and coordination in an organism?
Solution:
Co-ordination in this sense refers to the regulation or control of body activity.
Plants need very little in the way of a control system. Since growth and reproduction are about the only things that are regulated, a rapid control system is not required and hormonal control is all they possess.

Animals are continually moving through new environments that may pose all types of changes and threatening situations to the organism. This requires the rapid and precise control of a nervous system. Hormones regulate slower activities, such as growth, development and reproduction.

Question 6
How are involuntary actions and reflex actions different from each other?
Solution:
All reflex actions are involuntary in nature but all involutary actions are not reflexes as the beating of heart is an involuntary action but is not reflex action.

Reflex actions are very quick but all involutary actions may not be very fast as in heart beating.
A reflex action may involve any muscle or a gland as we withdraw our hand on touching a hot object but all involuntary actions involve only smooth i.e., involuntary or cardiac muscles.

Reflex actions are at the level of spinal cord whereas the involuntary actions generally involve brain too.
Nerves and autonomious nervous system can increase or decrease the rate of involuntary actions but reflex actions can be controlled by great will only and are not usually controllable.

Reflex actions are done to meet emergencies where as an inv.action may or may not be for just meeting an emergency but may be a critical lie process as circulation of blood, swallowing of food, movement of food in food pipe, etc.

Multiple Choice Questions (MCQs) [1 Mark each]

Question 1.
What is the correct direction of flow of electrical impulses ? [NCERT Exemplar]

Answer:
(c) Direction of flow of electrical impulse.
Impulse → Dendrite → Cell body → Axon → Release of chemicals that cross synapse → Dendrite of next neuron.

Question 2.
Three directions in which nerve impulses can travel in the nervous system are listed below:
(i) Away from the central nervous system
(ii) Towards the central nervous system
(iii) Within the central nervous system
In which direction do impulses in sensory and relay (intermediate) neurons travel?

	Sensory Neuron	Relay Neuron
(a)	(i)	(ii)
(b)	(i)	(iii)
(c)	(ii)	(i)
(d)	(ii)	(iii)

Answer:
(d) Sensory neuron transmits impulses towards CNS, (i.e. brain and spinal cord) while, the relay neurons occur within the CNS and serve as links between other neurons.

Question 3.
In a nerve pathway, the following events take place in a coordinated order.
(i) Activation of muscle
(ii) Activation of receptor
(iii) Passage of impulses along a motor neuron
(iv) Passage of impulses along a sensory neuron
Read the events given and identify the correct order of these events from the table given below:

First	→		Last
(a)	(ii)	(iii)	(iv)	(i)
(b)	(ii)	(iv)	(iii)	(i)
(c)	(iv)	(i)	(iii)	(ii)
(d)	(iv)	(ii)	(i)	(iii)

Answer:
(b) The sequence of events in a typical nerve pathway is receptor → passage of impulse along sensory neuron → passage of impulse along motor neuron → activation of muscle (effector). Thus, the correct sequence is (ii), (iv), (iii) and (i).

Question 4.
The diagram shows a section of the brain and different parts labelled as W,X, Y and Z.

Study the figure and correlate the regions which control balance, heart rate and temperature in human body?

	Balance	Heart Rate	Temperature
(a)	W	Z	X
(b)	X	Y	Z
(c)	Y	X	W
(d)	Z	W	Y

Answer:
(b) Out of the options given, the region X, (i.e. cerebellum) controls balance, region Y (i.e. medulla oblongata) controls heartbeat and region Z, (i.e. hypothalamus) controls temperature in human body.

Question 5.
Which of the following endocrine glands is unpaired? [NCERT Exemplar]
(a) Adrenal
(b) Testes
(b) Pituitary
(d) Ovary
Answer:
(c) There are two adrenal glands, one on top of each kidney that make adrenaline hormone. Testes are paired glands present in males and secrete male sex hormone. Pituitary gland is present just below the brain and is unpaired. It is also called master gland as it secretes a number of hormones. Ovaries are paired glands present in females and secrete female sex hormones.

Question 6.
Dramatic changes of body features associated with puberty are mainly because of secretion of [NCERT Exemplar]
(a) oestrogen from testes and testosterone from ovary
(b) oestrogen from adrenal gland and testosterone from pituitary gland
(c) testosterone from testes and oestrogen from ovary
(d) testosterone from thyroid gland and oestrogen from pituitary gland
Answer:
(c)

Gland	Hormone		Function
Testes (only in males)	Testosterone		To control the development of male sex organs and male features such as deep voice, etc., i.e. changes associated with puberty.
Ovaries (only in females)	Oestrogen		To control the development of female sex organs and female features such as soft skin, etc.
	Progesterone	To control uterus changes during menstrual cycle and helps in maintenance of pregnancy.

Class 10 Science Control and Coordination Mind Map

Coordination is the process through which two or more organs interact and complement the functions of one another. The neural system & endocrine system jointly coordinate & regulate the physiological functions in the body. The neural system provides an organised network of point-to-point connections for a quick coordination. The endocrine system provides chemical integration through hormones.

Animal Nervous System
The neural system of all animals is composed of highly specialized cells called neurons which can detect, receive & transmit different kinds of stimuli. They are specialized for conducting information via electrical impulses from one part of the body to another.

Structure and Function of Neuron

It is a structural & functional unit of neural system and is composed of three major parts:
Ceil body contains cytoplasm with typical cell organelles like nucleus etc.
Dendrites: Short fibres which branch repeatedly & project out of the cell body. These fibres transmit impulses towards the cell body.
Axon is a long fibre, the distal end of which is branched and forms nerve ending. Nerve endings possess synaptic vesicles containing chemicals called neurotransmitters.

Transmission of impulses:

Stimulus or information from the environment is detected by specialized tips of some nerve cells called as receptors.
Dendritic tip acquire all these information and sets off a chemical reaction.
This chemical reaction then creates an electric impulse that travels from the dendrite to the cell body, and then along the axon to its end.
At the end of the axon, the electrical impulse sets off the release of some chemicals (neurotransmitters). These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron.
A similar synapse finally allows delivery of such impulses from neurons to other cells, such as muscles cells or gland.

The human neural system is divided into two parts:

Central neural system (CNS) includes the brain & spinal cord and is the site of information processing & control.
Peripheral neural system (PNS) comprises of all nerves of body associated with CNS (brain and spinal cord). The nerve fibres of PNS are of two types: cranial nerves (arising from the brain) and spinal nerves (arising from the spinal cord).

Brain

It is the main coordinating centre of the body. The bra in and spinal cord constitute the CNS. They receive information from al 1 parts of the body and integrate it.
The brain is located in bony box called as cranium or skull which protects the brain. Spinal cord is protected with the help of vertebral column. In addition, cerebrospinal fluid also covers the brain and the spinal cord which provide the function of shock absorption.
The brain has three such major parts or regions, namely the fore-brain, mid-brain and hind-brain.
Fore-brain: It is the main thinking part of the brain. It consists of cerebrum, hypothalamus etc.
- Function: interpret information received from sensory receptors.
- Control the movement of voluntary muscles.
- It also contains centre associated with hunger which gives us the sensation of feeling full.
Midbrain: It serves important function in few involuntary movements, movements of the eye, auditory and visual processing.
Hindbrain: It consists of pons, medulla, and cerebellum.
- Function: Medulla controls involuntary actions such as blood pressure, salivation and vomiting.
- Cerebellum is responsible for precision of voluntary actions and maintaining the posture and balance of the body.

Reflex Action

The entire process of response to a peripheral nervous stimulation that occurs involuntarily (without conscious effort or thought) and requires the involvement of a part of central nervous system is called a reflex action.
Reflex action decreases the duration of action by bypassing the thinking and processing step.
It does so by linking the nerves carrying the signal (say the sensation of heat) directly to the nerves that move the muscle. These types of linkage or connection between input and output nerves are formed in the spinal cord.
These connections are called as reflex arc (sensory/input nerve-* Spinal cord -> motor/ output nerve)

Coordination In Plants

Plants have neither nervous system nor muscles. Their movements or responses are either growth dependent or growth independent.

Immediate Response To Stimulus Or Growth Independent

The plants also use electrical-chemical means to convey information from cell to cell, but unlike in animals, there is no specialised tissue in plants for the conduction of information.

Secondly, plant cells change shape by changing the amount of water in them, resulting in swelling or shrinking. In contrast, animal muscle cells have special proteins that change both their shape and their arrangement in the cell in response to nervous electrical impulses.

Example: folding up and drooping of leaves of chhui-mui (the ‘sensitive’ or ‘touch-me-not’ plant of the Mimosa family) in response to touch.

Movement Due To Growth

The movement of a plant in response to the stimulus is called as tropism. The movement in the direction of the response is called as positive tropism and movement away from the stimulus is termed as negative tropism.

Types:

Phototropism: Bending of plant in response to the light e.g. movement of sunflowers in response to day or night.
Geotropism: Movement of plant in response to gravity. Shoots show negative geotropism and roots show positive geotropism.
Chemotropism: Movement of plant in response to chemical as observed in case of growth of pollen tube.
Hydrotropism: e.g. roots beneath the Earth’s surface bend in the direction of underground w^ater.
Other example may include the climbing of tendrils in response to touch. When they come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This causes the tendril to circle around the object and thus cling to it.

Plant Hormones

There are five main types of plant hormones or growth regulators:

Auxins: Helps in cell elongation and thus phototropism, geotropism, and other plant responses.
Gibberellins: Stimulate growth of the stem and flowering.
Cytokinins: They cause cell division, enlargement, and organ formation. They are present in greater concentration in areas of rapid cell division, such as in fruits and seeds.
Ethylene: Promotes ripening of fruits.
Abscisic acid: Inhibits growth and causes wilting of leaves and fruits.

Hormones In Animals

Hormones are non-nutrient chemicals which act as intercellular messengers & are produced in trace amounts. The timing and amount of hormone released are regulated by feedback mechanisms Examples:

Adrenaline: Secreted from adrenal gland which prepare the body for fight or flight situation.
Thyroxin: Secreted from thyroid gland and regulates carbohydrate, protein and fat metabolism so as to provide the best balance for growth.
Deficiency of iodine in diet may cause hypo-secretion of thyroxin which results in goiter.
Growth hormones which regulate growth and. development of the body are secreted from
pituitary gland.
Hyper-secretion may cause gigantism and hypo-secretion may cause dwarfism.
Testosterone in males and oestrogen in females lead to changes take place during puberty’.
Insulin produced by pancreas regulates the blood sugar level in the body.

NCERT Solutions for Class 10 Science Chapter 7 Control and Coordination (Hindi Medium)

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NCERT Solutions for Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables Ex 3.5

March 6, 2026

Get Free NCERT Solutions for Class 10 Maths Chapter 3 Ex 3.5 PDF. Pair of Linear Equations in Two Variables Class 10 Maths NCERT Solutions are extremely helpful while doing your homework. Exercise 3.5 Class 10 Maths NCERT Solutions were prepared by Experienced LearnCBSE.in Teachers. Detailed answers of all the questions in Chapter 3 Maths Class 10 Pair of Linear Equations in Two Variables Exercise 3.5 provided in NCERT TextBook.

Topics and Sub Topics in Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables:

Section Name	Topic Name
3	Pair of Linear Equations in Two Variables
3.1	Introduction
3.2	Pair Of Linear Equations In Two Variables
3.3	Graphical Method Of Solution Of A Pair Of Linear Equations
3.4	Algebraic Methods Of Solving A Pair Of Linear Equations
3.4.1	Substitution Method
3.4.2	Elimination Method
3.4.3	Cross-Multiplication Method
3.5	Equations Reducible To A Pair Of Linear Equations In Two Variables
3.6	Summary

You can also download the free PDF of Ex 3.5 Class 10 Pair of Linear Equations in Two Variables NCERT Solutions or save the solution images and take the print out to keep it handy for your exam preparation.

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Maths
Chapter	Chapter 3
Chapter Name	Pair of Linear Equations in Two Variables
Exercise	Ex 3.5
Number of Questions Solved	4
Category	NCERT Solutions

NCERT Solutions for Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables Ex 3.5

NCERT Solutions for Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables Ex 3.5 are part of NCERT Solutions for Class 10 Maths. Here we have given NCERT Solutions for Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables Exercise 3.5

Ex 3.5 Class 10 Maths Question 1.
Which of the following pairs of linear equations has unique solution, no solution or infinitely many solutions. In case there is unique solution, find it by using cross-multiplication method.
(i) x – 3y – 3 = 0, 3x – 9y – 2 = 0
(ii) 2x + y = 5, 3x + 2y = 8
(iii) 3x – 5y = 20, 6x – 10y = 40
(iv) x – 3y – 7 = 0, 3x – 3y – 15 = 0
Solution:

Download NCERT Solutions For Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables PDF

Ex 3.5 Class 10 Maths Question 2.
(i) For which values of a and b does the following pair of linear equations have an infinite number of solutions?
2x + 3y = 7
(a – b)x + (a + b)y = 3a + b – 2
(ii) For which value of k will the following pair of linear equations have no solution?
3x + y = 1
(2k – 1)x + (k – 1)y = (2k + 1)
Solution:

Ex 3.5 Class 10 Maths Question 3.
Solve the following pair of linear equations by the substitution and cross-multiplication methods:
8x + 5y = 9, 3x + 2y = 4
Solution:

Ex 3.5 Class 10 Maths Question 4.
Form the pair of linear equations in the following problems and find their solutions (if they exist) by any algebraic method:
(i) A part of monthly hostel charges is fixed and the remaining depends on the number of days one has taken food in the mess. When a student A takes food for 20 days she has to pay ₹ 1000 as hostel charges, whereas a student B, who takes food for 26 days, pays ₹ 1180 as hostel charges. Find the fixed charges and the cost of food per day.
(ii) A fraction becomes \(\frac { 1 }{ 3 }\) when 1 is subtracted from the numerator and it becomes \(\frac { 1 }{ 4 }\) when 8 is added to its denominator. Find the fraction.
(iii) Yash scored 40 marks in a test, getting 3 marks for each right answer and losing 1 mark for each wrong answer. Had 4 marks been awarded for each correct answer and 2 marks been deducted for each incorrect answer, then Yash would have scored 50 marks. How many questions were there in the test?
(iv) Places A and B are 100 km apart on a highway. One car starts from A and another from B at the same time. If the cars travel in the same direction at different speeds, they meet in 5 hours. If they travel towards each other, they meet in 1 hour. What are the speeds of the two cars?
(v) The area of a rectangle gets reduced by 9 square units, if its length is reduced by units and breadth is increased by 3 units. If we increase the length by 3 units and the breadth by 2 units, the area increases by 67 square units. Find the dimensions of the rectangle.
Solution:

NCERT Solutions for Class 10 Maths Chapter 3 Pairs of Linear Equations in Two Variables (Hindi Medium) Ex 3.5

NCERT Solutions for Class 10 Maths

We hope the NCERT Solutions for Class 10 Maths Chapter Pair of Linear Equations in Two Variables Ex 3.5, help you. If you have any query regarding NCERT Solutions for Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables Exercise 3.5, drop a comment below and we will get back to you at the earliest.

NCERT Solutions for Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables Ex 3.7

March 6, 2026

Get Free NCERT Solutions for Class 10 Maths Chapter 3 Ex 3.7 PDF. Pair of Linear Equations in Two Variables Class 10 Maths NCERT Solutions are extremely helpful while doing your homework. Exercise 3.7 Class 10 Maths NCERT Solutions were prepared by Experienced LearnCBSE.in Teachers. Detailed answers of all the questions in Chapter 3 Maths Class 10 Pair of Linear Equations in Two Variables Exercise 3.7 provided in NCERT TextBook.

Topics and Sub Topics in Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables:

Section Name	Topic Name
3	Pair of Linear Equations in Two Variables
3.1	Introduction
3.2	Pair Of Linear Equations In Two Variables
3.3	Graphical Method Of Solution Of A Pair Of Linear Equations
3.4	Algebraic Methods Of Solving A Pair Of Linear Equations
3.4.1	Substitution Method
3.4.2	Elimination Method
3.4.3	Cross-Multiplication Method
3.5	Equations Reducible To A Pair Of Linear Equations In Two Variables
3.6	Summary

You can also download the free PDF of Ex 3.7 Class 10 Pair of Linear Equations in Two Variables NCERT Solutions or save the solution images and take the print out to keep it handy for your exam preparation.

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Maths
Chapter	Chapter 3
Chapter Name	Pair of Linear Equations in Two Variables
Exercise	Ex 3.7
Number of Questions Solved	8
Category	NCERT Solutions

NCERT Solutions for Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables Ex 3.7

NCERT Solutions for Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables Ex 3.7 are part of NCERT Solutions for Class 10 Maths. Here we have given NCERT Solutions for Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables Exercise 3.7

Ex 3.7 Class 10 Maths Question 1.
The age of two friends Ani and Biju differ by 3 years. Ani’s father Dharam is twice as old as Ani and Biju is twice as old as his sister Cathy. The ages of Cathy and Dharam differ by 30 years. Find the ages of Ani and Biju.
Solution:
Let the ages of Ani and Biju be x years and y years respectively.
If Ani is older than Biju
x – y =3
If Biju is older than Ani
y – x = 3
-x + y =3 [Given]

Subtracting equation (i) from equation (ii), we get:
3x – 57
⇒ x = 19
Putting x = 19 in equation (i), we get
19-y = 3
⇒ y = 16
Again subtracting equation (iv) from equation (iii), we get
3x = 63
⇒ x = 21
Putting x = 21 in equation (iii) we get
21 -y= -3
⇒ y = 24
Hence, Ani’s age is either 19 years or 21 years and Biju’s age is either 16 years or 24 years.

Download NCERT Solutions For Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables PDF

Ex 3.7 Class 10 Maths Question 2.
One says, “Give me a hundred, friend! I shall then become twice as rich as you”. The other replies, “If you give me ten, I shall be six times as rich as you”. Tell me what is the amount of their (respective) capital?
Solution:
Let the two friends have ₹ x and ₹ y.
According to the first condition:
One friend has an amount = ₹(x + 100)
Other has an amount = ₹ (y – 100
∴ (x + 100) =2 (y – 100)
⇒ x + 100 = 2y – 200
⇒ x – 2y = -300       …(i)
According to the second condition:
One friend has an amount = ₹(x – 10)
Other friend has an amount =₹ (y + 10)
∴ 6(x – 10) = y + 10
⇒ 6x – 60 = y + 10
⇒ 6x-y = 70                                        …(ii)
Multiplying (ii) equation by 2 and subtracting the result from equation (i), we get:
x – 12x = – 300 – 140
⇒ -11x = -440
⇒ x = 40
Substituting x = 40 in equation (ii), we get
6 x 40 – y = 70
⇒ -y = 70- 24
⇒ y   = 170
Thus, the two friends have ₹ 40 and ₹ 170.

Ex 3.7 Class 10 Maths Question 3.
A train covered a certain distance at a uniform speed. If the train would have been 10 km/h faster, it would have taken 2 hours less than the scheduled time. And, if the train were slower by 10 km/h, it would have taken 3 hours more than the scheduled time. Find the distance covered by the train.
Solution:
Let the original speed of the train be x km/h
and the time taken to complete the journey be y hours. ‘
Then the distance covered = xy km

Case I: When speed = (x + 10) km/h and time taken = (y – 2) h
Distance = (x + 10) (y – 2) km
⇒ xy = (x + 10) (y – 2)
⇒ 10y – 2x = 20
⇒ 5y – x = 10
⇒ -x + 5y = 10 …(i)

Case II: When speed = (x – 10) km/h and time taken = (y + 3) h
Distance = (x – 10) (y + 3) km
⇒ xy = (x – 10) (y + 3)
⇒ 3x- 10y = 30 …(ii)
Multiplying equation (i) by 3 and adding the result to equation (ii), we get
15y – 10y = 30 f 30
⇒ 5y = 60
⇒ y   = 12
Putting y = 12 in equation (ii), we get
3x- 10 x 12= 30
⇒ 3x   = 150
⇒ x   = 50
∴ x = 50 and y = 12
Thus, original speed of train is 50 km/h and time taken by it is 12 h.
Distance covered by train = Speed x Time
= 50 x 12 = 600 km.

Ex 3.7 Class 10 Maths Question 4.
The students of a class are made to stand in rows. If 3 students are extra in a row, there would be 1 row less. If 3 students are less in a row, there would be 2 rows more. Find the number of students in the class.
Solution:
Let the number of rows be x and the number of students in each row be y.
Then the total number of students = xy
Case I: When there are 3 more students in each row
Then the number of students in a row = (y + 3)
and the number of rows = (x – 1)
Total number of students = (x – 1) (y + 3)
∴ (x – 1) (y + 3) = xy
⇒ 3x -y =3 …(i)
Case II: When 3 students are removed from each row
Then the number of students in each row = (y-3)
and the number of rows = (x + 2)
Total number of students = (x + 2) (y – 3)
∴ (x + 2) (y – 3) = xy
⇒ -3x + 2y = 6 …(ii)
Adding the equations (i) and (ii), we get
-y + 2y = 3 + 6
⇒ y = 9
Putting y = 9 in the equation (ii), we get
-3x + 18 = 6
⇒ x = 4
∴ x = 4 and y = 9
Hence, the total number of students in the class is 9 x 4 = 36.

Ex 3.7 Class 10 Maths Question 5.
In a ∆ABC, ∠C = 3 ∠B = 2(∠A + ∠B). Find the three angles.
Solution:
Let ∠A = x° and ∠B = y°.
Then ∠C = 3∠B = (3y)°.
Now ∠A + ∠B + ∠C = 180°
⇒ x + y + 3y = 180°
⇒ x + 4y = 180° …(i)
Also, ∠C = 2(∠A + ∠B)
⇒ 3y – 2(x + y)
⇒ 2x – y = 0° …(ii)
Multiplying (ii) by 4 and adding the result to equation (i), we get:
9x = 180°
⇒ x = 20°
Putting x = 20 in equation (i), we get:
20 + 4y = 180°
⇒ 4y = 160°
⇒ y = \(\frac { 160 }{ 40 }\) = 40°
∴ ∠A = 20°, ∠B = 40° and ∠C = 3 x 40° = 120°.

Ex 3.7 Class 10 Maths Question 6.
Draw the graphs of the equations 5x – y = 5 and 3x – y = 3. Determine the coordinates of the vertices of the triangle formed by these lines and the y-axis.
Solution:
5x – y = 5 …(i)
3x-y = 3 …(ii)
For graphical representation:
From equation (i), we get: y = 5x – 5
When x = 0, then y -5
When x = 2, then y = 10 – 5 = 5
When x = 1, then y = 5 – 5 = 10
Thus, we have the following table of solutions:

From equation (ii), we get:
⇒ y = 3x – 3
When x = 0, then y = -3
When x = 2, then y = 6 – 3 = 3
When x = 1, then y = 3 – 3 = 0
Thus, we have the following table of solutions:

Plotting the points of each table of solutions, we obtain the graphs of two lines intersecting each other at a point C(1, 0).

The vertices of ΔABC formed by these lines and the y-axis are A(0, -5), B(0, -3) and C(1, 0).

Ex 3.7 Class 10 Maths Question 7.
Solve the following pairs of linear equations:

Solution:
(i) The given equations are
px + qy = p – q …(1)
qx – py = p + q …(2)
Multiplying equation (1) byp and equation (2) by q and then adding the results, we get:
x(p² + q²) = p(p – q) + q(p + q)

(ii) The given equations are
ax + by = c …(1)
bx – ay = 1 + c …(2)
Multiplying equation (1) by b and equation (2) by a, we get:
abx + b²y = cb …(3)
abx + a²y = a(1+ c) …(4)
Subtracting (3) from (4), we get:

(iii) The given equations may be written as: bx – ay = 0 …(1)
ax + by = a² + b² …(2)
Multiplying equation (1) by b and equation (2) by a, we get:
b²x + aby = 0 ….(3)
a²x + aby = a(a² + b²) …..(4)
Adding equation (3) and equation (4), we get:
(a² + b²)x = a (a² + b²) a(a² + b²)

(iv) The given equations may be written as:
(a – b)x + (a + b)y = a² – 2ab – b² …(1)
(a + b)x + (a + b)y = a² + b² …(2)
Subtracting equation (2) from equation (1), we get:
(a – b)x – (a + b)x
= (a² – 2ab – b²) – (a² + b²)
⇒ x(a – b- a-b) = a² – 2ab – b² – a² – b²⇒ -2bx = -2ab – 2b²⇒ 2bx = 2b² + 2ab

(v) The given equations may be written as:
76x – 189y = -37 …(1)
-189x + 76y = -302 …(2)
Multiplying equation (1) by 76 and equation (2) by 189, we get:
5776x – 14364y = -2812 …(3)
-35721x + 14364y = -57078 …(4)
Adding equations (3) and (4), we get:
5776x – 35721x = -2812 – 57078
⇒ – 29945x = -59890
⇒ x = 2
Putting x = 2 in equation (1), we get:
76 x 2 – 189y = -37
⇒ 152 – 189y = -37
⇒ -189y = -189
⇒ y = 1
Thus, x = 2 and y = 1 is the required solution.

Ex 3.7 Class 10 Maths Question 8.
ABCD is a cyclic quadrilateral (see figure). Find the angles of the cyclic quadrilateral.

Solution:

NCERT Solutions for Class 10 Maths Chapter 3 Pairs of Linear Equations in Two Variables (Hindi Medium) Ex 3.7

NCERT Solutions for Class 10 Maths

We hope the NCERT Solutions for Class 10 Maths Chapter Pair of Linear Equations in Two Variables Ex 3.7, help you. If you have any query regarding NCERT Solutions for Class 10 Maths Chapter 3 Pair of Linear Equations in Two Variables Exercise 3.7, drop a comment below and we will get back to you at the earliest.