Sound ICSE Class-7th Concise Selina Physics Solutions

Sound ICSE Class-7th Concise Selina Physics Solutions Chapter-6. We Provide Step by Step Answer of Objective, True False , Fill in the blanks, Match the following , Short / Long Answer, Numerical s of Exercise-6 Sound. Visit official Website  CISCE  for detail information about ICSE Board Class-7.

Sound ICSE Class-7th Concise Selina Physics Solutions Chapter-6


A. Objective Questions Chapter-6 Sound ICSE Concise Selina

1. Write true or false for each statement

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(a) Sound can travel in vacuum.
Answer. False.
Correct — Sound requires medium to travel.

(b) Sound is a form of energy.
Answer. True.

(c) Sound can only be produced by vibrating bodies.
Answer. True.

(d) Larger is the amplitude, feeble is the sound.
Answer.False.
Correct — Larger the amplitude, greater is the sound.

(e) The frequency is measured in hertz.
Answer. True.

(f) Loudness depends on frequency.
Answer. False.
Correct — Loudness depends on the amplitude.

(g) Waveforms of two different stringed instruments can be the same.
Answer. False.
Correct—Waveforms of two different stringed instruments cannot be the same.

(h) Female voice is shriller than the male voice.
Answer. True.

(i) A ticking clock sound is heard late when heard through a metal.
Answer. False.
Correct—A ticking clock sounds is heard early when heard through a metal.


2. Fill in the blanks Sound ICSE Class-7th Concise

(a) Sound is produced when a body vibrates.
(b) The number of times a body vibrates in one second is called its frequency.
(c) The pitch of a sound depends on its frequency.
(d) Sound can travel in a medium solid, liquid or gas.
(e) We can hear sounds of frequency in the range of 20 Hz to 20,000 Hz.
(f) Sound requires a medium for propagation.
(g) Sound travels faster in solids than in liquids.
(h) The sound heard after reflection is echo.
(i) Sound produces sensation in ears


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3. Match the following Sound ICSE Class-7th Concise

Match the following


4. Select the correct alternative Sound ICSE Class-7th Concise

(a) We can distinguish a shrill sound from a flat sound by its

amplitude
loudness
pitch
none of the above.

Answer

pitch
(b) We can hear sound of frequency

10 Hz
500 Hz
100,000 Hz
50,000 Hz

Answer

500 Hz

(c) Sound cannot travel in

gases
liquids
solids
vacuum

Answer

vacuum
(d) The minimum distance required between the source and the reflector so as to hear the echo in air is

10m
17m
34 m
50 m

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Answer

17m

(e) Wavelength is measured in

kg
second
litre
metre

Answer

metre

(f) The speed of sound in water is

332 m
1500 m
5000 m s
1000 m s

Answer

1500 m
(g) Sound travels the fastest in

liquids
solids
gases
vacuum

Answer

solids


B. Short/Long Answer Questions Sound ICSE Class-7th Concise

Question 1.

What do you mean by a vibratory motion ?
Answer:
The oscillatory motion in which the body assumes a new shape during its motion, is called the vibratory motion.

Question 2.

What is sound ?
Answer:
Sound is a form of energy which produces the sensation of hearing.

Question 3.

How is sound produced ?
Answer:
Sound is produced by vibrating bodies.

Question 4.

Describe an experiment to show that each source of sound is a vibrating body.
Answer:
Sound is produced when a body vibrates. In other words, each source of sound is a vibrating body. This can be demonstrated by the following experiment.
Take a ruler. Press its one end on the table with the left hand as shown in figure. Pull down the other end of the ruler with the right hand and then leave it.
You will notice that the ruler vibrates i.e., the ruler moves to and fro and a humming sound is heard.

After some time, the ruler stops vibrating. No sound is then heard.

After some time, the ruler stops vibrating. No sound is then heard.

Question 5.

Name two sources of sound.
Answer:
Each vibrating body is a source of sound. We, the human beings, produce sound when our vocal cords vibrate on blowing air through them by our lungs. Some animals like birds, frogs etc., also produce sound due to vibration of their vocal cords. But bees do not have the voice-boxes. They produce sound by moving their wings up and down very fast.

Question 6.

How do we produce sound ?
Answer:
Our throat has a larynx. The voice is produced in the larynx. Larynx is also called the voice box. It is designed to produce voice. It is a box like structure with walls of tough tissues. Inside two folds of the tissue, there is a gap. They are the vocal cords. When we breathe, the vocal cords become loose and the gap between them increases. When we talk, shout or sing, the cords become tight and hence they vibrate, thus produce sound. Given figure shows the part of the body which vibrates to produce sound.

Question 7.

The bees do not have voice-boxes. How do they produce sound ?
Answer:
The bees do not have the voice-boxes. Still they produce sound.
This happens by the vibrations produced by the quick movement of their wings. Bees buzz while flying and depositing pollen among flowers.

Question 8.

Can sound travel through a vacuum ? Describe an experiment to explain your answer.
Answer:
Experiment — Arrange an electric bell, a glass bell jar, a vacuum pump, a battery and a switch as shown in the figure. When the circuit is closed by pressing the switch, the bell starts ringing and sound can be heard. Now remove the air from the jar with the help of vacuum pump. The loudness of the sound gradually decreases and a stage comes when no sound is heard. Sound requires a medium to travel but cannot travel in vacuum

Connect the bell to a battery through a switch. On pressing the switch, the bell starts ringing and a sound is heard. The sound reaches us through the air in the jar.
Now start the vacuum pump. It withdraws the air from the jar. You will notice that as the jar is evacuated, the sound becomes feeble and feeble. After some time when no air is left within the jar, no sound is heard. However, the hammer of the electric bell can be still seen striking the gong. The reason is that when no air is left in the jar, the sound does not reach us, although the bell is still ringing (or vibrating).
Thus, sound cannot travel through a vacuum.

Question 9.

Describe an experiment to show that sound can travel in water.
Answer:
Take a tub filled with water. Hold a bell in one hand and dip it in water. Keep one of your ears gently on the surface of water without letting water into the ear. Now ring the bell inside water. You will be able to hear the sound clearly. This shows that sound can travel through liquids.

Question 10.

Describe an experiment to show that sound can travel in a solid.
Answer:
Take two empty ice-cream cups. Make a small hole at the bottom of each cup and pass a long thread (about 20 m long) through them. Tie a knot or match-stick at each end of the thread so that the thread does not slip out through the holes. This makes a toy – telephone

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