Page 1 - HA CH 15 CLASS XI

PHYSICS, CLASS 11

HOME ASSIGNMENT ON CHAPTER-15(WAVES)

1. i) Obtain an expression for velocity of sound in air using Newton’s formula.
ii) What is the discrepancy in the calculated values and how it is overcome by Laplaces
formula.
2. Compare and contrast between progressive and Stationary waves.
st
nd
3. What do you mean by organ pipe? Find expression for frequency of 1 and 2 harmonic
in case of open and closed organ pipe of identical dimension?
4. What do you mean by beats? Obtain an expression for beat frequency.
5. What is meant by Doppler’s effect of sound? Find the apparent frequency when
i) When source is moving towards stationary observer.
ii) When source is moving towards stationary observer.
6. What happens to velocity of sound with temperature and pressure?
7. Write the wave equation of a progressive wave in different forms. Write the relation
between wave velocity and phase velocity. Define wave number.
8. Find the frequency of vibrations of stationary transverse wave in different harmonics in

case of a stretched string.
9. A steel wire has a length of 12.0 m and a mass of 2.10 kg. What should
be the tension in the wire so that speed of a transverse wave on the wire

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equals the speed of sound in dry air at 2 0°C = 340 ms .
10. A train, standing at the outer signal of a railway station blows a whistle
of frequency 400 Hz in still air. (i) What is the frequency of the whistle
for a platform observer when the train (a) approaches the platform with
a speed of 10 ms~1. (b) recedes from the platform with a speed of 10 ms -
(ii) What is the speed of sound in each case? The speed of sound in still
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air can be taken as 340 ms .