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NCERT Exemplar Class 6 Science Chapter 15 Air Around Us are part of NCERT Exemplar Class 6 Science. Here we have given NCERT Exemplar Class 6 Science Solutions Chapter 15 Air Around Us.

NCERT Exemplar Class 6 Science Solutions Chapter 15 Air Around Us

Multiple Choice Questions

Question 1.
Which of the following statements is incorrect?
(a) All living things require air to breathe.
(b) We can feel air but we cannot see it.
(c) Moving air makes it possible to fly a kite.
(d) Air is present everywhere but not in soil.
Solution:
(d): Air is omnipresent and is present in the soil also. This can be proved by a simple activity where a lump of dry soil is taken in a beaker or a glass. When water is added to the soil, it displaces the air which is seen in the form of bubbles.

Question 2.
Wind does not help in the movement of which of the following?
(a) Firki
(b) Weathercock
(c) Ceiling fan
(d) Sailing yacht
Solution:
(c): Ceiling fan moves by electricity, and hence, wind does not help in the movement of ceiling fan.

Question 3.
What is not true about air?
(a) It makes the windmill rotate.
(b) It helps in the movements of aeroplanes.
(c) Birds can fly due to presence of air.
(d) It has no role in water cycle.
Solution:
(d) : Air plays a major role in water cycle. Air helps the water vapour to rise up to form clouds. Evaporation of water, cloud formation and falling of rain, all take place in the atmosphere.

Question 4.
Mountaineers carry oxygen cylinders with them because
(a) there is no oxygen on high mountains
(b) there is deficiency of oxygen on mountains at high altitude
(c) oxygen is used for cooking
(d) oxygen keeps them warm at low temperature.
Solution:
(b): With increase in altitude, the atmosphere gets thinner and the supply of oxygen is reduced. This causes difficulty in breathing on hill stations and mountains. Therefore, while climbing high mountains, mountaineers carry oxygen cylinders with them.

Question 5.
Boojho took an empty plastic bottle, turned it upside down and dipped its open mouth into a bucket filled with water. He then tilted the bottle slightly and made the following observations.
(i) Bubbles of air came out from the bottle.
(ii) Some water entered the bottle.
(iii) Nitrogen gas came out in the form of bubbles and oxygen got dissolved in water.
(iv) No bubbles formed, only water entered the bottle.
Which observations is / are correct?
(a) (i) and (ii)
(b) (iv) only
(c) (iii) and (iv)
(d) (i) only
Solution:
(a)

Question 6.
Which of the following components of air is present in the largest amount in the atmosphere?
(a) Nitrogen
(b) Oxygen
(c) Water vapour
(d) Carbon dioxide
Solution:
(a) Atmosphere cpntains 78% nitrogen, 21% oxygen and remaining 1% is formed by carbon dioxide, water vapour, few other gases and dust particles. Thus, atmosphere contains nitrogen in the largest amount.

Question 7.
The components of air which are harmful to living beings are
(a) nitrogen and carbon dioxide
(b) dust and water vapour
(c) dust and smoke
(d) smoke and water vapour.
Solution:
(c) Water vapour, nitrogen and carbon dioxide are useful to living beings. Water vapour is important for the water cycle in nature. Nitrogenisnecessaryforplants. Carbon dioxide is essential for photosynthesis.

Question 8.
Ushatooka lump of dry soil in a glass and added water to it till it was completely immersed. She observed bubbles coming out. The bubbles contain
(a) water vapour
(b) only oxygen gas
(c) air
(d) none of these.
Solution:
(c) When the water is poured on the lump of soil, it displaces the air trapped in it which is seen in the form of bubbles.

Very Short Answer Type Questions

Question 9.
State whether the following statements are true or false. If false, correct them.
(a) Plants consume oxygen for respiration.
(b) Plants produce oxygen during the process of making their own food.
(c) Air helps in the movements of sailing yachts and gliders but plays no role in the flight of birds and aeroplanes.
(d) Air does not occupy any space.
Solution:
(a) True
(b) True
(c) False – Air helps in the movement of sailing yachts and gliders and also helps in the flight of birds and aeroplanes.
(d) False – Air does occupies space.

Question 10.
In a number of musical instruments, air plays an important role. Can you name such instruments?
Solution:
Air plays an important role in a number of musical instruments such as flute, trumpet, mouth organ, shehnai and harmonium.

Question 11.
In the boxes of column I the letters of some words got jumbled. Arrange them in proper form in the boxes given in column II.

Solution:

Question 12.
Make sentences using the given set of words.
(a) 99%, oxygen, nitrogen, air, together
(b) Respiration, dissolved, animals, air aquatic
(c) Air, wind, motion, called
Solution:
(a) Oxygen and nitrogen together make up 99% of the air.
(b) Aquatic animals use dissolved air for respiration.
(c) Air in motion is called wind.

Short Answer Type Questions

Question 13.
A list of words is given in a box. Use appropriate words to fill up the blanks in the following statements.
[Air, oxygen, wind, water vapour, mixture, combination, direction, road, bottles, cylinders]
(a) The ______ makes the windmill rotate.
(b) Air is a ______ of some gases.
(c) A weather cock shows the in which the air is moving at that place.
(d) Mountaineers carry oxygen ___ with them, while climbing high mountains.
Solution:
(a) wind
(b) mixture
(c) direction
(d) cylinders

Question 14.
Observe the picture given in Fig. 15.1 carefully and answer the following questions.

(a) What is covering the nose and mouth of the policeman?
(b) Why is he putting a cover on his nose?
(c) Can you comment on air quality of the place shown in the Fig.15.1?
Solution:
(a) The policeman is wearing a mask to cover his nose and mouth.
(b) He puts a cover on his nose to protect himself from dirt and polluted air. A mask avoids exposure to the harmful exhaust of vehicles, thus prevents the harmful gases and dust particles entering our body.
(c) The given figure shows a polluted area where the air quality is not good. It is due to the smoke and harmful gases such as carbon monoxide and sulphur dioxide emitted by the automobiles along with dust particles present in the air.

Question 15.
Garima observed that when she left her tightly capped bottle full of water in open sunlight, tiny bubbles were formed all around inside the bottle. Help Garima to know why it happened?
Solution:
Air dissolved in water starts escaping in the form of tiny bubbles due to heat from the sun. Thus, tiny bubbles were formed all around inside the bottle.

Question 16.
Match the items of column I with the items of column II.

Solution:
(a) – (iv)
(b) – (iii)
(c) – (v)
(d) – (i)
(e) – (ii)

Long Answer Type Questions

Question 17.
Explain the following observations very briefly.
(a) A firki does not rotate in a closed area.
(b) The arrow of weather cock points towards a particular direction at a particular moment.
(c) An empty glass in fact is not empty.
(d) Breathing through mouth may harm you.
Solution:
(a) A firki or pmwheel rotates when placed in an open area due to the moving air present all around. In a closed area, there is a lack of air movement which does not support the rotation of a firki.
(b) A weather cock is an instrument used for indicating the direction of the wind. It consists of an arrow, mounted at its centre of gravity so it can move freely about a vertical axis. Therefore, the arrow points towards a particular direction at a particular moment to show the latest direction of the wind movement.
(c) An empty glass is filled with the air. ft is filled completely with air even if turned upside down. It can be proved with a simple experiment in which an empty bottle is turned upside down in a beaker filled with water. The water does not enter the bottle when it is pushed’in an inverted position because there is no space for air to escape. When the bottle is tilted, the air is able to escape out in the form of bubbles and water fills up the empty space. This shows that even an empty glass is filled with the air.
(d) Air contains some gases, water vapour and dust particles. When air is inhaled through nostrils, the fine hair and mucus present in the nose prevent dust particles from entering the respiratory tract. But, if we breathe through mouth, the harmful dust particles may enter our body and make us ill. Thus, breathing through mouth may harm us.

Question 18.
Write just a few sentences for an imaginary situation if any of the following gases disappear from the atmosphere.
(a) Oxygen
(b) Nitrogen
(c) Carbon dioxide
Solution:
(a) If oxygen gas disappeared from the atmosphere, life would not be possible on earth as the presence of oxygen is essential for the survival of the living organisms. Animals and plants take in oxygen from the atmosphere and release carbon dioxide during respiration. Even the aquatic plants and animals take up oxygen in the dissolved form for breathing. It would not be possible for organisms to breathe in the absence of oxygen and hence, eventually the organisms will die.
(b) Nitrogen constitutes major part i.e. 78% of the atmosphere and it does not support burning. If nitrogen gas disappeared from the atmosphere, things on earth will bum very fast which may produce disastrous results. Moreover, nitrogen is required by plants for their growth, although plants are not able to absorb the nitrogen directly from the air. They ocnsume it in the soluble form either through fertilisers or by converting it into nitrate compounds which are absorbed by the plants through soil. Nitrogen is also present in some amounts in all the proteins. All living things need protein for their growth. Thus, if nitrogen gets disappeared from the atmosphere, plants, animals, humans and other organisms would not be able to grow properly and may eventually die.
(c) Although carbon dioxide is present in traces (0.03%) in the atmosphere, it plays a major role in the survival of living beings. Plants require carbon dioxide to manufacture their own food by the process of photosynthesis. During this process, oxygen in evolved out. This maintains the carbon dioxide oxygen balance in the air. If carbon dioxide gets disappeared from the atmosphere, the plants will not be able to produce their food and oxygen will not be released which will disturb the carbon dioxide – oxygen ratio in the atmosphere. In the absence of oxygen and food, there will be no life on earth.

Question 19.
Paheli kept some water in a beaker for heating. She observed that tiny bubbles appeared before the water started to boil. She boiled the water for about 5 minutes and filled it in a bottle up to the brim and kept the bottle air tight till it cooled down to room temperature.
(a) Why did the tiny bubbles appeared?
(b) Do you think tiny bubbles will appear on heating the water taken out from the bottle? Justify your answer.
Solution:
(a) The tiny bubbles appeared before the water started to boil due to the air dissolved in water. On heating, the air dissolved in water escaped in the form of bubbles.
(b) The tiny bubbles will appear on heating the water taken out from the bottle as on opening the cap, some amount of air will be trapped in it. Some amount of air will also be trapped during the transfer of water from the bottle to the utensil for heating. Since the amount of trapped air will be less in the poured water, there will be less number of bubbles appearing in the water on heating as compared to the previous one.

Question 20.
On a Sunday morning Paheli’s friend visited her home. She wanted to see some flowering plants in the nearby garden. Both of them went to the garden. While returning from the garden they also observed some flowering plants on the road side. But to their surprise they found that the leaves and flowers of these roadside plants were comparatively very dull. Can you help them to know why?
Solution:
The dull appearance of the leaves and flowers of the roadside plants may be due to the djust and soot particles emitted from the vehicles, chimneys and factories. These particles might have got deposited on the plant parts which made them appear dull.

We hope the NCERT Exemplar Class 6 Science Chapter 15 Air Around Us will help you. If you have any query regarding NCERT Exemplar Class 6 Science Solutions Chapter 15 Air Around Us, drop a comment below and we will get back to you at the earliest.

NCERT Exemplar Class 6 Science Chapter 13 Fun with Magnets are part of NCERT Exemplar Class 6 Science. Here we have given NCERT Exemplar Class 6 Science Solutions Chapter 13 Fun with Magnets.

NCERT Exemplar Class 6 Science Solutions Chapter 13 Fun with Magnets

Multiple Choice Questions 

Question 1.
Observe the pictures A and 8 given in figure carefully.

Which of the following statement is correct for the above given pictures?
(a) In A, cars 1 and 2 will come closer and in B, cars 3 and 4 will come closer.
(b) In A, cars 1 and 2 will move away from each other and in B, cars 3 and 4 will move away.
(c) In A, cars 1 and 2 will move away and in 8,3 and 4 will come closer to each other.
(d) In A, cars 1 and 2 will come closer to each other and in 8,3 and 4 will move away from each other.
Solution:
(d) Unlike poles attract each other while like poles repel each other.

Question 2.
The arrangement to store two magnets is shown by figures (a), (b), (c) and (d). Which one of them is the correct arrangement?

Solution:
(b)

Question  3.
Three magnets A, B and C were dipped one by one in a heap of iron filing. Figure shows the amount of the iron filing sticking to them.

The strength of these magnets will be
(a) A > B > C
(b) A < B < C
(c) A = B = C
(d) A < B > C
Solution:
(a): The amount of the iron filing sticking to magnets is directly proportional to their strengths.

Question 4.
North pole of a magnet can be identified by
(a) Another magnet having its poles marked as North pole and South pole.
(b) Another magnet no matter whether the poles are marked or not.
(c) Using an iron bar.
(d) Using iron filings.
Solution:
(a): That pole of the magnet which is repelled by the north pole of the given magnet will be considered as north pole of the magnet.

Question 5.
A bar magnet is immersed in a heap of iron filings and pulled out. The amount of iron filing clinging to the
(a) North pole is almost equal to the south pole.
(b) North pole is much more than the south pole.
(c) North pole is much less than the south pole.
(d) Magnet will be same all along its length.
Solution:
(a): Magnetic strengths of north pole and south pole of a magnet is same.

Very Short Answer Type Questions

Question 6.
Fill in the blanks.
(i) When a bar magnet is broken; each of the broken part will have _________ pole/poles.
(ii) In a bar magnet, magnetic attraction is _____ near its ends.
Solution:
(i) two
(ii) more

Question 7.
Paheli and her friends were decorating the class bulletin board. She dropped the box of stainless steel pins by mistake. She tried to collect the pins using a magnet. She could not succeed. What could be the reason for this?
Solution:
The pins are made of stainless steel which is a non-magnetic material.

Question 8.
How will you test that ‘tea dust’ is not adulterated with iron powder?
Solution:
By using a magnet we can test that tea dust’ is not adulterated with iron powder. If it has iron powder it will stick to the magnet.

Question 9.
Boojho dipped a bar magnet in a heap of iron filings and pulled it out. He found that iron filings got stuck to the magnet as shown in figure.

(i) Which regions of the magnet have more iron filings sticking to it?
(ii)What are these regions called?
Solution:
(i) The ends of the magnet have more iron filings attached to it.
(ii) These regions are called poles of the magnet.

Short Answer Type Questions

Question 10.
Four identical iron bars were dipped in a heap of iron filings one by one. Figure shows the amount of iron filings sticking to each of them.

(a) Which of the iron bar is likely to be the strongest magnet?
(b) Which of the iron bars is not a magnet? Justify your answer.
Solution:
(a) Iron bar (a) is likely to be the strongest magnet as amount of iron filings sticking to it, is much more than other bars.
(b) Iron bar (b) is not a magnet because iron filings do not stick to it.

Question 11.
A toy car has a bar magnet laid hidden inside its body along its length. Using another magnet i how will you find out which pole of the magnet is facing the front of the car?
Solution:
If the front of the toy car gets attracted to the north pole of the given magnet then it is the south pole of the bar magnet hidden inside the car and vice-versa.

Question 12.
Match column I with column II (One option of I can match with more than one option of II.

Solution:
(a) – (ii) , (iii) and (iv)
(b) – (iii)
(c) – (i)
(d) – (iii)

Question 13.
You are provided with two identical metal bars. , One out of the two is a magnet. Suggest two ways to identify the magnet.
Solution:
There can be following ways to identify the magnet out of the two identical metal bars :
(i) By freely suspending the metal bars. Magnet will rest along a particular direction.
(ii) By attracting iron filings.
(iii) By using another magnet. Like poles will repel each other while unlike poles will attract each other.

Long Answer Type Questions

Question 14.
Three identical iron bars are kept on a table. Two out of three bars are magnets. In one of the magnet the North-South poles are marked. How will you find out which of the other two bars is a magnet? Identify the poles of this magnet.
Solution:
The magnet on which the North-South poles are marked can be used to find out the magnet out of two bars.
The magnet with known poles will attract and repel two ends of a magnet while it will attract both the ends of an ordinary bar. This process is known as test for repulsion. To find out the poles of unknown magnet, we can use the same test. North pole marked on the given magnet will repel the north pole of unknown magnet.

Question 15.
Describe the steps involved in magnetising an iron strip with the help of a magnet.
Solution:
An iron strip can be magnetised by rubbing it with a magnet in a particular direction again and again as shown in figure.

Magnets can also be made with the help of electricity.

Question 16.
Figure shows a magnetic compass. What will happen to the position of its needle if you bring a bar magnet near it? Draw a diagram to show the effect on the needle on bringing the bar magnet near it. Also draw the diagram to show the effect when the other end of the bar magnet is brought near it.

Solution:
The magnetic needle of the compass will get deflected.

Question 17.
Suggest an activity to prepare a magnetic compass by using an iron needle and a bar magnet.
Solution:
To prepare a magnetic compass, the given iron needle is magnetised by rubbing a bar magnet over it repeatedly in a particular direction. After that it may be set in a way so that it can rotate freely when suspended. Hence, the iron needle can act as compass and give north-south direction.

Question 18.
Boojho kept a magnet close to an ordinary iron bar. He observed that the iron bar attracts a pin as shown in figure.

What inference could he draw from this observation? Explain.
Solution:
He could infer from this observation that the magnetic properties are induced into the iron bar and it acts like a magnet till the magnet is kept near it.

Question 19.
A bar magnet is cut into two pieces A and B, from the middle, as shown in figure.

Will the two pieces act as individual magnets? Mark the poles of these two pieces. Suggest an activity to verify your answer.
Solution:
Yes, the two pieces A and B will act as individual magnets. A magnet will always have two poles – north and south pole. Each piece will have two poles.

By the test of repulsion, we can conclude that these two pieces A and B will act as individual magnets.

Question 20.
Suggest an arrangement to store a U shaped magnet. How is this different from storing a pair of bar magnets?
Solution: U shaped magnet – One metal plate is placed across the two poles of the U shaped magnet to store it.

Bar magnet – Two metal plates and one wooden block is used and arranged as shown in the figure.

We hope the NCERT Exemplar Class 6 Science Chapter 13 Fun with Magnets will help you. If you have any query regarding NCERT Exemplar Class 6 Science Solutions Chapter 13 Fun with Magnets, drop a comment below and we will get back to you at the earliest.

NCERT Exemplar Class 6 Science Chapter 12 Electricity and Circuits are part of NCERT Exemplar Class 6 Science. Here we have given NCERT Exemplar Class 6 Science Solutions Chapter 12 Electricity and Circuits.

NCERT Exemplar Class 6 Science Solutions Chapter 12 Electricity and Circuits

Multiple Choice Questions

Question 1.
Choose from the options a, b, c and d given in the figure which shows the correct direction of current .

Solution:
(b): In an electric circuit, the direction of current is taken to be from the positive terminal to the negative terminal of the electric cell.

Question 2.
Choose the incorrect statement.
(a) A switch is the source of electric current in a circuit.
(b) A switch helps to complete or break the circuit.
(c) A switch helps us to use electricity as per our requirement.
(d) When the switch is open there is an air gap between its terminals.
Solution:
(a) : An electric cell is the source of electric current in a circuit.

Question 3.
In an electric bulb, light is produced due to the glowing of
(a) the glass case of the bulb
(b) the thin filament
(c) the thick wires supporting the filament
(d) gases inside glass case of the bulb.
Solution:
(b)

Question 4.
In the following arrangement shown in figure, the bulb will not glow if the ends A and B are connected with

(a) A steel spoon
(b) A metal clip
(c) A plastic clip
(d) A copper wire
Solution:
(c): Plastic clip is an insulator. It does not conduct electricity.

Question 5.
In the circuit shown in figure, when the switch is moved to’ON’ position,

(a) the bulb A will glow first
(b) the bulb B will glow first
(c) the bulb C will glow first
(d) all bulbs will glow together.
Solution:
(d): As soon as the circuit gets completed, current is found at every point in the circuit instantly.

Question 6.
Filament of a torch bulb is
(a) a metal case
(b) metal tip at the centre of the base
(c) two thick wires
(d) a thin wire.
Solution:
(d)

Question 7.
Paheli is running short of connecting wires. To complete an electric circuit, she may use a
(a) glass bangle
(b) thick thread
(c) rubber pipe
(d) steel spoon.
Solution:
(d): Steel spoon is a good conductor of electricity.

Question 8.
In which of the following circuits A, B and C given in figure, the cell will be used up very rapidly?

Solution:
In circuit A, the cell will be used up very rapidly.

Question 9.
Figure shows a bulb with its different parts marked as 1,2,3,4 and 5. Which of them label the terminals of the bulb?

Solution:
Labels 3 and 4 are the terminals of the bulb.

Short Answer Type Questions

Question 10.
You are provided with a bulb, a cell, a switch and some connecting wires. Draw a diagram to show the connections between them to make the bulb glow.
Solution:

Question 11.
Will the bulb glow in the circuit shown in figure ? Explain.

Solution:
No, the bulb will not glow in this circuit because the switch is open and the circuit is incomplete. Current flows only in a closed circuit.

Question 12.
An electric bulb is connected to a cell through a switch as shown in figure. When the switch is brought in ‘ON’ position, the bulb does not glow. What could be the possible reason/s for it? Mention any two of them.

Solution:
There could be following reasons for it:
(i) Cell is a used one.
(ii) Bulb is fused.
(iii) Loose connections.
(iv) Break in connecting wires.

Question 13.
A torch requires 3 cells. Show the arrangement of the cells, with a diagram, inside the torch so that the bulb glows.
Solution:

Question 14.
When the chemicals in the electric cell are used up, the electric cell stops producing electricity. The electric cell is then replaced with a new one. In case of rechargeable batteries (such – as the type used in mobile phones, camera and inverters), they are used again and again. How?
Solution:
Rechargeable batteries can be recharged • by providing them appropriate current. These are called secondary cells or storage cells.

Question 15.
Paheli connected two bulbs to a cell as shown f in figure,

She found that filament of bulb B is broken. Will the bulb A glow in this circuit? Give reason.
Solution:
No, the bulb will not glow in this circuit as the filament of bulb B is broken. So the circuit remains incomplete.

Question 16.
Why do bulbs have two terminals?
Solution:
Bulb consists of a tiny thin wire called filament. Bulb has two terminals to connect the filament within the circuit so that current can pass through it.

Question 17.
Which of the following arrangement A, B, C and D given in figure should not be set up? Explain, why?

Solution:
Arrangement A is not desirable and should not be set up. This will exhaust the cell very quickly as large current will flow through it.

Question 18.
A fused bulb does not glow. Why?
Solution:
In a fused bulb, the filament is broken and the circuit is incomplete.

Question 19.
Paheli wanted to glow a torch bulb using a cell. She could not get connecting wires, instead, she got two strips of aluminium foil. Will she succeed? Explain, how?
Solution:
Yes, she will succeed as aluminium foil strips can act as connecting wires being good conductor of electricity.

Long Answer Type Questions

Question 20.
Boojho has a cell and a single piece’ of connecting wire. Without cutting the wire in two, will he be able to make the bulb glow? Explain with the help of a circuit diagram.
Solution:
Yes, using the arrangement given in figure, he can succeed in getting the bulb glow.

He can connect second terminal of the bulb directly to the positive terminal of the cell as given in figure. In this way, circuit will get completed without using another piece of connecting wire.

Question 21.
Figure A and B, show a bulb connected to a cell in two different ways.

(i) What will be the direction of the current through the bulb in both the cases (Q to P orPto Q)?
(ii) Will the bulb glow in both the cases?
(iii) Does the brightness of the glowing bulb depend on the direction of current through it?
Solution:
(i) In case A: Q toP
In case B: P to Q
(ii) Yes, the bulb will glow in both the cases as the circuit is complete in both the cases.
(iii) No, the brightness of the glowing bulb does not depend on the direction of current through it.

Question 22.
Think of six activities which use electric current. Also name the devices used to perform the activity.
Example:

Solution:

Question 23.
A torch is not functioning, though contact points in the torch are in working condition. What can be the possible reasons for this? Mention any three.
Solution:
The possible reasons could be
(i) the bulb may be fused.
(ii) the cells may have been used up.
(iii) the cells are not placed in the correct order.
(iv) the switch is faulty.

We hope the NCERT Exemplar Class 6 Science Chapter 12 Electricity and Circuits will help you. If you have any query regarding NCERT Exemplar Class 6 Science Solutions Chapter 12 Electricity and Circuits, drop a comment below and we will get back to you at the earliest.

NCERT Exemplar Class 6 Science Chapter 11 Light, Shadows and Reflections are part of NCERT Exemplar Class 6 Science. Here we have given NCERT Exemplar Class 6 Science Solutions Chapter 11 Light, Shadows and Reflections.

NCERT Exemplar Class 6 Science Solutions Chapter 11 Light, Shadows and Reflections

Multiple Choice Questions

Question 1.
Observe the picture given in figure carefully.

A patch of light is obtained at B, when the torch is lighted as shown. Which of the following is kept at position A to get this patch of light?
(b) A glass sheet
(c) A mirror
(d) A sheet of white paper,
Solution:
Only a mirror can reflect a patch of light and change its direction.

Question 2.
A student observes a tree given in figure through a pinhole camera. Which of the diagrams given in figures (a) to (d), depicts the image seen by her correctly?


Solution:
(b:) She will observe upside down image of the tree with lateral inversion.

Question 3.
Four students A, B, C and D looked through pipes of different shapes to see a candle flame as shown in figure.

Who will be able to see the candle flame clearly?
(a) A
(b) B
(c) C
(d) D
Solution:
(d): Light travels in a straight line.

Question 4.
Which of the following is/are not always necessary to observe a shadow?
(a) Sun
(b) Screen
(c) Source of light
(d) Opaque object
Solution:
(a): Sun is a source of light. Any source of light can replace it. So, sun is not always necessary to observe a shadow.

Question 5.
Paheli observed the shadow of a tree at 8:00 a.m., 12:00 noon and 3:00 p.m. Which of the following statements is closest to her observation about the shape and size of the shadow?
(a) The shape of the shadow of the tree changes but the size remains the same.
(b) The size of the shadow of the tree changes but the shape remains the same.
(c) Both the size and shape of the shadow of the tree change.
(d) Neither the shape nor the size of the shadow changes.
Solution:
(c): Sun is source of light here and it changes its position at different points of time. So accordingly size and shape of the shadow of the tree change.

Question 6.
Which of the following can never form a circular shadow?
(a) A ball
(b) A flat disc
(c) A shoe box
(d) An ice cream cone
Solution:
(c)

Question 7.
Two students while sitting across a table looked down on to its top surface. They noticed that they could see their own and each other’s image. The table top is likely to be made of
(a) unpolished wood
(b) red stone
(c) glass sheet
(d) wood top covered with cloth
Solution:
(c): Out of the given options, only glass sheet can reflect light properly in order to form their images.

Very Short Answer Type Questions

Question 8.
You have 3 opaque strips with very small holes of different shapes as shown in figure. If you obtain an image of the sun on a wall through these holes, will the image formed by these holes be the same or different?

Solution:
Same image will be formed by these holes. These opaque strips will act as pinholes and image of the sun will be obtained on wall.

Question 9.
Observe the picture given in figure. A sheet of some material is placed at position ‘P’, still the patch of light is obtained on the screen. What is the type of material of this sheet?

Solution:
Sheet P must be of transparent material as it allows light to pass through it.

Question 10.
Three torches A, B and C shown in figure are switched on one by one. The light from which of the torches will not form a shadow of the ball on the screen.

Solution:
The light from torch C will not form a shadow of the ball on the screen. Torch C is parallel to the screen and light travels in straight line.

Question 11.
Look at the given figure.

Will there be any difference in the shadow formed on the screen in A and B ?
Solution:
No, shadows formed on the screens A and B will be same.

Question 12.
Correct the following statements.
(i) The colour of the shadow of an object depends on its colour of the object.
(ii) Transparent objects allow light to pass through them partially.
Solution:
(i) The colour of the shadow of an object does not depend on its colour of the object.
(ii) Translucent objects allow light to pass through them partially or transparent objects allow most of the light to pass through them.

Question 13.
Suggest a situation where we obtain more than one shadow of an object at a time.
Solution:
At a time we can obtain more than one shadow of an object if light from more than one source falls on it.
For example: While watching a match in a stadium, we can observe multiple shadows of players.

Question 14.
0n a sunny day, does a bird or an aeroplane flying high in the sky cast its shadow on the ground? Under what circumstances can we see their shadow on the ground?
Solution:
Even on a sunny day, a bird or an aeroplane flying high in the sky does not cast its shadow on the ground.
We can see their shadow on the ground only if they are flying very close to the ground. In this case, ground acts as screen.

Question 15.
You are given a transparent glass sheet. Suggest any two ways to make it translucent without breaking it.
Solution:
(i) By applying oil, grease, butter on it or pasting a butter paper on it.
(ii) Grinding (rubbing) the surface of the glass by any abrasive material.

Question 16.
A torch is placed at two different positions A and B, one by one, as shown in figure.

The shape of the shadow obtained in two positions is shown in figure.

Match the position of the torch and shape of the shadow of the ball.
Solution:
A  → a; B → b
As the position of torch changes, we can observe the change in shape of shadow.

Question 17.
A student covered a torch with red cellophane sheet to obtain red light. Using the red light she obtains a shadow of an opaque object. She repeats this activity with green and blue light. Will the colour of the light affect the shadow? Explain.
Solution:
Maim The colour of light will not affect the shadow because shadow is the dark patch r formed when an object obstructs the path of
light and hence no light reaches in the shadow region.

Question 18.
Is air around us always transparent? Discuss.
Solution:
Mann Air around us is transparent but when thick smoke/ thick clouds, etc. are present in ‘ the air it does not remain transparent.

Question 19.
Three identical towels of red, blue and green colour are hanging on a clothesline in the sun. ‘ What would be the colour of shadows of these
towels?
Solution:
The colour of shadows of all the three t towels will be same as no light passes through them. Shadow will be of black colour.

Question 20.
Using a pinhole camera a student observes the image of two of his friends, standing in sunlight, wearing yellow and red shirt respectively. What will be the colours of the shirts in the image?
Solution:
The colours of the image of the shirts 1 will be the same as the colour of the shirt. Image obtained using a pinhole camera is inverted.

Question 21.
In figure, a flower made of thick coloured paper has been pasted on the transparent glass sheet.What will be the shape and colour of shadow seen on the screen?

Solution:
The shadow formed will be dark and of the shape of the flower along with the stalk.

Long Answer Type Questions

Question 22.
A football match is being played at night in a stadium with flood lights ON. You can see the shadow of a football kept at the ground but cannot see its shadow when it is kicked high in the air. Explain.
Solution:
We can see the shadow of football lying on the ground because the ground acts as a screen for it. However, when the football is kicked high, the ground, which is acting as a screen is away from the football, hence no shadow of the football will be formed on the ground.

Question 23.
A student had a ball, a screen and a torch in working condition. He tried to form a shadow of the ball on the screen by placing them at different positions. Sometimes the shadow was not obtained. Explain.
Solution:
Some of the reason can be
(i) The screen is far away from the ball.
(ii) The beam of light from the torch is falling parallel to the screen on the ball.
(iii) The torch is kept away from the ball.

Question 24.
A sheet of plywood, a piece of muslin cloth and that of a transparent glass, all of the same size and shape were placed at A one by one in the arrangement shown in figure. Will the shadow be formed in each case. If yes, how will the shadow on the screen be different in each case? Give reasons for your answer.

Solution:
Shadow will not be formed in each case. Only the piece of muslin cloth and the sheet of plywood will cast shadow on the screen.
The sheet of plywood will form a dark shadow as it blocks the path of light completely. The piece of muslin cloth will form a lighter shadow as it allows light to pass through it partially. The transparent glass will allow most of the light to pass through it. So, no shadow will be obtained on screen.

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