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Selina solutions Selina ICSE Concise Physics for Class 10 chapter 7 Sound

Chapters

Selina Selina ICSE Concise Physics Class 10

Selina ICSE Concise Physics for Class 10

Chapter 7 - Sound

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Define amplitude term in relation to a wave.

Define frequency term in relation to a wave.

Define wavelength term in relation to a wave.

Define wave velocity term in relation to a wave.

A wave passes from one medium to another medium. Mention the property of the wave which changes.

A wave passes from one medium to another medium. Mention the property of the wave which does not change.

State two factors on which the speed of a wave travelling in a medium depends.

State two differences between the light and sound waves.

What is meant by an echo?

What is the condition necessary for an echo to be heard distinctly?

A man is standing at a distance of 12 m from a cliff. Will he be able to hear a clear echo? Give a reason for your answer.

State two applications of echo.

Explain how the speed of sound can be determined by the method of echo.

State the use of echo by a bat, dolphin and fisherman.

How do bats avoid obstacles in their way, when in flight?

What is meant by sound ranging?

Give one use of sound ranging.

Name the waves used for sound ranging. Why are the waves mentioned by you audible to us?

What is sonar? State the principle on which it is based.

Name the waves which are used in sonar to find the depth of a sea. Give one reason for their use.

State the use of echo in medical science.

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The minimum distance between the source and the reflector in air. So that an echo is heard is approximately equal to:

(a) 10 m (b) 17 m (c) 34 m (d) 50 m

To detect the obstacles in their path, bats produce:
(a) infrasonic waves (b) ultrasonic waves
(c) electromagnetic waves (d) radio waves

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The wavelength of waves produces on the surface of water is 20 cm. If the wave velocity is 24 m s-1, calculate: (i) the number of waves produces in one second , and (ii) the time in which one wave is produced.

Calculate the minimum distance in air required between the source of sound and the obstacle to hear an echo. Take speed of sound in air = 350 m s-1

What should be the minimum distance between source and reflector in water so that echo is heard distinctly?
(The speed of sound in water = 1400 m s-1)

A man standing 25 m away from a wall produces a sound and receives the reflected sound. (a) Calculate the time after which he receives the reflected sound if the speed of the sound in air is 350 m s-1. (b) will the man be able to hear a distinct echo? Explain the answer.

A radar sends a signal to an aeroplane at a distance 45 km away with a speed of 3 × 108 m s -1. After how much time is the signal received back from the aeroplane?

A man standing 48 m away from a wall fires a gun calculate the time after which an echo is heard. (The speed of sound in air is 320 m s -1).

A ship on the surface of water sends a signal and receives it back froma a submarine inside water after 4 s. Calculate the distance of the submarine from the ship. (The speed of sound in water is 1450 m s-1)

A pendulum has a frequency of 5 vibrations per second. An observer starts the pendulum and fires a gun simultaneously. He hears echo from the cliff after 8 vibrations of the pendulum. If the velocity of sound in air is 340 m s-1, find the distance between the cliff and the observer.

A person standing between the two vertical cliffs produces a sound. Two successive echoes are heard at 4 s and 6 s. Calculate the distance between the cliffs.
(speed of sound in air = 320 m s-1)

A man fires a gun and hears its echo after 5 s. The man then moves 310 m towards the hill and fires his gun again. This time he hears the echo after 3 s. calculate the speed of sound.

On sending an ultrasonic wave from a ship towards the bottom of a sea, the time interval between sending the wave and receiving it back is found to be 1.5 s. If the velocity of wave in sea water is 1400 m s-1, find the depth of the sea.

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What do you understand by free vibrations of a body?

What is meant by the natural frequency of vibration of a body?

On What factors does the natural frequency of vibration of a body depend?

Draw a graph between displacement from mean position and time for a body executing free vibrations in vacuum.

State one condition for a body to execute free vibrations.

Name one factors on which the frequency of sound emitted due to vibrations in an air column depends.

State one way of increasing the frequency of a note produced by an air column.

State two ways of increasing the frequency of vibrations of a stretched string.

What adjustments would you make for tuning a stringed instrument for it to emit a note of a desired frequency?

The diagram below in Fig. 7.11 shoes three ways in which the string of an instrument can vibrate.

(a) which of the diagram shows the principal note?
(b) which has the frequency four times that of the first?
(c) what is the ratio of the frequency of the vibration in (i) and (ii)?

Explain why strings of different thicknesses are provided on a stringed instrument.
[Hint : Natural frequency of vibration of a stretched string is inversely proportional to the radius (or thickness) of string so notes of different frequencies can be produces by vibrating different strings.]

A blade, fixed at one end, is made to vibrate by pressing its other end and then releasing it. State one way in which the frequency of vibrations of the blade can be lowered.

How does the medium affect the amplitude of free vibrations of a body?

What are damped vibrations? How do they differ from free vibrations? Give one example of each.

The diagram in Fig. 7.12 shows the displacement – time graph of vibrating body.

(i) name the kind of vibrations
(ii) Give one example of such vibrations
(iii) why is the amplitude of vibrations gradually decreasing?
(iv) what happens to the vibrations of the body after some time?

A tuning fork is set into vibration in air. Name the kind of vibrations it executes.

Draw a sketch showing the displacement of a body executing damped vibrations against time.

What are forced vibrations? 

Give one example to illustrate forced vibrations.

Distinguish between the free (or natural) and forced vibrations.

What is meant by resonance?

Describe a simple experiment to illustrate the phenomenon of resonance and explain it.

State the condition for the occurrence of resonance.

Complete the following sentence:
Resonance is a special case of …………….. vibrations, when frequency of the driving force is ……… natural frequency of the body.

Differentiate between the forced and resonant vibrations.

Why is a loud sound heard at resonance?

Fig 7.13 shows two tuning forks A and B of the same frequency mounted on separate sound boxes with their open ends facing each other. The fork A is set into vibration. (a) Describe your observation. (b) state the principle illustrated by this experiment.

In fig . 7.14 A, B, C and D are four pendulums suspended from the same elastic string XY. Lengths of pendulum A and D are equal, while the length of pendulum B is smaller and the pendulum C is longer. The pendulum A is set into vibration.
(a) what is your observation? (b) Give reason for your observation.

A vibrating tuning fork held over an air column of a given length with its one end closed, produces a loud audible sound. Name the phenomenon responsible for it and explain the observation.

In Fig. 7.15, A, B , C and D represent test tube each of height 20 cm which are filled with water up to heights of 12 cm, 14 cm, 16cm and 18cm respectively. If a vibrating tuning fork is placed over the mouth if test tube D, a loud sound is heard.

(a) Describe the observations with the tubes A, B and C when the vibrating tuning fork is placed over the mouth of these tubes.
(b) Give the reason for your observation in each case.
(c) State the principle illustrated by the above experiment.

When a troop crosses a suspension bridge the soldiers are asked to break steps. Explain the reason.

Why are the stringed instruments like guitar provided with a hollow sound box?

How do you tune your radio set to a particular station?

Name the phenomenon involved in tuning your radio set to a particular station  and define it.

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MUTIPLE CHOICE TYPE:
A wire stretched between two fixed supports, is plucked exactly in the middle and then released. It executes (neglect the resistance of the medium):
(a) resonant vibrations (b) free vibrations
(c) damped vibrations (d) forced vibrations

MUTIPLE CHOICE TYPE:
When a body vibrates under a periodic force, the vibrations of the body are:
(a) free vibrations (b) damped vibrations
(c) forced vibration (d) resonant vibrations

A tuning fork of frequency 256 Hz will resonate with another tuning fork of frequency:
(a) 128 Hz (b) 256 Hz
(c) 384 Hz (d) 512 Hz

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Name three characteristics of a musical sound.

(a) Which of the following quality determines the loudness of a sound wave?
(i) wavelength (ii) frequency and (iii) amplitude
(b) How is loudness related to the quantity mentioned above in part(a)?

If the amplitude of a wave is doubled, what will be the effect on its loudness?

Two waves of the same pitch have amplitudes in the ratio 1:3. What will be the ratio of loudness?

Two waves of the same pitch have amplitudes in the ratio 1:3. What will be the ratio of frequencies?

How does the wave pattern of a loud note differ from a soft note? Draw a diagram.

Name the unit in which loudness of sound is measured.

Why is the loudness of the sound heard by a plucked wire increased when it is mounted on a sound board?

Define the term intensity of a sound wave. State the unit in which it is measured.

How is loudness of sound related to the intensity of wave producing it?

Comment on the statement ‘loudness of sound is a subjective quantity, while intensity is an objective quantity.

State three factors on which loundess of sound heard by a listener depends.

Name the unit used to measure the sound level.

What is the safe limit of sound level in dB for our ears?

What is meant by noise pollution?

Name one source of sound causing noise pollution.

What determines the pitch of a sound?

Name the subjective property of sound related to its frequency.

Name and define the characteristic which enables one to distinguish two sounds of same loudness, but of different frequencies, given by the same instrument.

Draw a diagram to show the wave pattern of high pitch note and a low pitch note, but of the same loudness.

How is it possible to detect the filling of a bottle under a water tap by hearing the sound at a distance?

The frequencies of notes given by flute, guitar and 500 Hz. Which one of these has the highest pitch?

Complete the following sentence:
The pitch of sound increases if its frequency …………..

Complete the following sentence:
 If the amplitude of a sound is halved, its loudness becomes ………………

Name the characteristic which enables one to distinguish the sound of two musical instruments even if they are of the same pitch and same loudness.

How does the two sounds of same loudness and same pitch produced by different instruments differ? Draw diagrams to illustrate your answer.

Two identical guitars are played by two persons to give notes of the same pitch. Will they differ in quality? Give a reason for your answer.

Two musical notes of the same pitch and same loudness are played on two different instruments. Their wave patterns are as shown in Fig. 7.24

Explain why the wave patterns are different.

How is it possible to recognize a person by his voice without seeing him?

State the factor that determine the pitch of a note.

State the factor that determine the loudness of the sound heard.

State the factor that determine the quality of the note.

Name the characteristic of the sound affected due to a change in its amplitude.

Name the characteristic of the sound affected due to a change in its wave form.

Name the characteristic of the sound affected due to a change in its frequency.

In what respect does the wave pattern of a noise and a music differ? Draw diagram to explain your answer.

The sketches I to IV in Fig. 7.25 show sound waves, all formed in the same time interval.

Which diagram shows
(i) a note from a musical instrument
(ii) a soft (not loud) note,
(iii) a bass (low frequency) note.

A microphone is connected to the Y-input of a C.R.O Three different sounds are made in turn in front of the microphone. Their traces (a), (b) and (c) produces on the screen are shown in Fig . 7.26

(i) which trace is due to the loudest sound? Give reason for your answer.
(ii) Which trace is due for the sound with the lowest pitch? Explain your answer.

State one difference between a musical note and a noise.

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MULTIPLE CHOICE TYPE:
By reducing the amplitude of a sound wave, its:
(a) pitch increases (b) loudness decreases
(c) loudness increases (d) pitch decreases

MULTIPLE CHOICE TYPE:

Two sounds of same loudness and same pitch produced by two different instruments differ in their:
(a) amplitudes (b) frequencies
(c) wave forms (d) all the above

MULTIPLE CHOICE TYPE:

Two sounds A and B are of same amplitude, same wave forms but of frequencies f and 2f respectively.
Then:
(a) B differ in quality from A
(b) B is grave, A is shrill
(c) B is shrill, A is grave
(d) B is louder than A.

Selina Selina ICSE Concise Physics Class 10

Selina ICSE Concise Physics for Class 10
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