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1. Thread

### when the train is far off but its sound cannot be heard through air. Why

When we put our ear to a railway track, we can hear the sound of an approaching train even when the train is far off but its sound cannot be heard...
Thread by: Vinila Choudary, Mar 23, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
2. Thread

### A powerful sound signal sent from a ship is received again after 2.4 seconds.

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Thread by: Vinila Choudary, Mar 23, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
3. Thread

### The boy hears the echo of his shout after 4.8 seconds. Find the speed of the sound.

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Thread by: Vinila Choudary, Mar 23, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
4. Thread

### A sound wave has a frequency 2 kHz and wavelength 40 cm. How long will it take to travel 1.6 km?

A sound wave has a frequency 2 kHz and wavelength 40 cm. How long will it take to travel 1.6 km? [ATTACH]
Thread by: Vinila Choudary, Mar 23, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
5. Thread

### calculate the distance of hill from the boy.

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Thread by: Vinila Choudary, Mar 23, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
6. Thread

### calculate the wavelength and frequency of new wave.

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Thread by: Vinila Choudary, Mar 23, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
7. Thread

### A longitudinal wave of wavelength 1 cm travels in air with a speed of 330 rn/s.

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Thread by: Vinila Choudary, Mar 23, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
8. Thread

### The wavelength of waves produced on the surface of water is 20 cm.

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Thread by: Vinila Choudary, Mar 23, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
9. Thread

### wavelength when frequency is 256 Hz.

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Thread by: Vinila Choudary, Mar 23, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
10. Thread

### Describe an activity to study the reflection of sound.

[ATTACH] To observe the reflection of sound, take a drawing board and fix it on the floor. Put two metallic or cardboard tubes as shown in Fig. These...
Thread by: Vinila Choudary, Mar 23, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
11. Thread

### Why do we hear the sound produced by the humming bees

Why do we hear the sound produced by the humming bees while the sound of vibrations of pendulum is not heard? Humming bees produce sound by...
Thread by: Vinila Choudary, Feb 29, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
12. Thread

### What is a sound board? Explain the working of a soundboard with the help of a labelled diagram.

The reflection of sound may take place at curved surfaces also. This fact is made use of in the large halls to spread sound evenly throughout the...
Thread by: Vinila Choudary, Feb 29, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
13. Thread

### What do you mean by an echo? State two conditions for hearing a distinct echo.

Conditions: (i) To hear a distinct echo, the time interval between the original sound and the reflected one must be at least 0.1 s. (ii) For...
Thread by: Vinila Choudary, Feb 29, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
14. Thread

### Explain the terms crests and troughs of a wave.

The elevation or hump in a transverse wave is called crest. It is that part of the transverse wave which is above the line of zero disturbance of the...
Thread by: Vinila Choudary, Feb 29, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
15. Thread

### What is a stethoscope? Name the principle on which a stethoscope works.

Stethoscope is a medical instrument used for listening sounds produced within the body, chiefly in the heart or lungs. Stethoscope works on the...
Thread by: Vinila Choudary, Feb 29, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
16. Thread

### What are transverse waves? Give two examples.

A wave in which the particles of the medium vibrate up and down at right angles to the direction in which the wave is moving. Examples: (i) The...
Thread by: Vinila Choudary, Feb 29, 2012, 0 replies, in forum: CBSE Class 9 Physics Help
17. Thread

### What are longitudinal waves? Give two examples.

The waves in which the particles of niedium oscillate to and fro from their mean position in the direction of propagation of waves are called...
Thread by: Vinila Choudary, Feb 29, 2012, 0 replies, in forum: CBSE Class 9 Physics Help