Balbharati solutions for Physics [English] 11 Standard Maharashtra State Board chapter 8 - Sound [Latest edition]

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A sound carried by air from a sitar to a listener is a wave of the following type.

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When sound waves travel from air to water, which of these remains constant?

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The Laplace’s correction in the expression for velocity of sound given by Newton is needed because sound waves

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Speed of sound is maximum in

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The walls of the hall built for music concerns should

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Wave motion is doubly periodic. Explain.

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What is Doppler effect?

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Describe a transverse wave.

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Define a longitudinal wave.

State Newton’s formula for the velocity of sound.

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What is the effect of pressure on the velocity of sound?

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What is the effect of humidity of air on velocity of sound?

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What do you mean by an echo?

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State any two applications of acoustics.

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Define amplitude.

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Define wavelength of a wave.

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Draw a wave and indicate points which are

1. in phase
2. out of phase
3. have a phase difference of `pi/2`

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Define the relation between velocity, wavelength and frequency of the wave.

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State and explain the principle of superposition of waves.

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State the expression for apparent frequency when source of sound and listener are

1. moving towards each other
2. moving away from each other

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State the expression for apparent frequency when the source is stationary and the listener is

1. moving towards the source
2. moving away from the source

State the expression for apparent frequency when listener is stationary and source is moving towards the listener.

State the expression for apparent frequency when listener is stationary and source is moving away from the listener.

Answer briefly.

Explain what is meant by phase of a wave.

Define progressive wave.

State any four properties of progressive wave.

State Newton’s formula for the velocity of sound.

What is the limitation of Newton's formula for velocity of sound?

Solve the following problem.

A certain sound wave in air has a speed 340 m/s and wavelength 1.7 m for this wave, calculate 

1. the frequency
2. the period

Solve the following problem.

A tuning fork of frequency 170 Hz produces sound waves of wavelength 2 m. Calculate the speed of sound.

Solve the following problem.

An echo-sounder in a fishing boat receives an echo from a shoal of fish 0.45 s after it was sent. If the speed of sound in water is 1500 m/s, how deep is the shoal?

Solve the following problem.

A girl stands 170 m away from a high wall and claps her hands at a steady rate so that each clap coincides with the echo of the one before.

1. If she makes 60 claps in 1 minute, what value should be the speed of sound in air?
2. Now, she moves to another location and finds that she should now make 45 claps in 1 minute to coincide with successive echoes. Calculate her distance for the new position from the wall.

Sound wave A has period 0.015 s, sound wave B has a period of 0.025 s. Which sound has greater frequency?

At what temperature will the speed of sound in the air be 1.75 times its speed at S.T.P?

At what temperature will the speed of sound in air be 1.75 times its speed at N.T.P?

Solve the following problem.

A man standing between 2 parallel cliffs fires a gun. He hears two echoes one after 3 seconds and other after 5 seconds. The separation between the two cliffs is 1360 m, what is the speed of sound?

Solve the following problem.

If the velocity of sound in air at a given place on two different days of a given week are in the ratio of 1:1.1. Assuming the temperatures on the two days to be same what quantitative conclusion can your draw about the condition on the two days?

Solve the following problem.

A police car travels towards a stationary observer at a speed of 15 m/s. The siren on the car emits a sound of frequency 250 Hz. Calculate the recorded frequency. The speed of sound is 340 m/s.

The sound emitted from the siren of an ambulance has a frequency of 1500 Hz. The speed of sound is 340 m/s. Calculate the difference in frequencies heard by a stationary observer if the ambulance initially travels towards and then away from the observer at a speed of 30 m/s.