Ncert Exemplar Solutions Class 8 Science Sound

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Ncert Exemplar Solutions Class 8 Science Sound

Welcome to NCTB Solutions. Here with this post we are going to help 8th class students for the Solutions of NCERT Exemplar Class 8 Science Book, Unit 13, Sound. Here students can easily find step by step solutions of all the problems for Sound, Also here our Science teacher’s are solved all the questions with easily understandable language with proper guidance so that all the students can understand easily.

Sound all Question Solutions :

Question no – (1)

A list of mediums is given below.

Answer :

Correct option – (d)

The sound can travel through air, water and vacuum.

Question no – (2)

The loudness of sound depends on

Answer :

Correct option – (a)

The loudness of sound depends on its amplitude.

Question no – (3)

Which of the following statements are correct?

Answer :

Correct option – (d) i, ii and iv only

Question no – (4)

An object is vibrating at 50 hertz. What is its time period?

Answer :

Correct option – (a)

0.02 s is its time period.

Question no – (5)

In order to reduce the loudness of a sound we have to

Answer :

Correct option – (c)

In order to reduce the loudness of a sound we have to decrease its amplitude of vibration of the sound.

Question no – (6)

Loudness of sound is measured in units of

Answer :

Correct option – (a)

Loudness of sound is measured in units of decibel (dB).

Question no – (7)

The loudness of sound is determined by the

Answer :

Correct option – (a)

The loudness of sound is determined by the amplitude of vibration.

Question no – (8)

1 hertz is equal to

Answer :

Correct option – (c)

1 hertz is equal to 60 vibrations per minute.

Question no – (9)

Pitch of sound is determined by its

Answer :

Correct option – (a)

Pitch of sound is determined by its Frequency.

Question no – (10)

Ultrasound has frequency of vibration

Answer :

Correct option – (c)

Ultrasound has frequency of vibration above 20,000 Hz.

Very Short Answer Questions :

Question no – (11)

Answer :

From the following information we could conclude that,

Speed of the sound wave in air = 330 m/s

Time taken for the sound to reach ears = 5s

So, distance where the lightning strike

= speed × time

= 330 × 5

= 1650 m.

Question no – (12)

Answer :

Yes, when we speak the Vocal Cords in our throat vibrates this vibrations are responsible for the sound that we make.

Question no – (13)

Answer :

Light and sound takes different time to reach a similar distance. In other word we could say light travels much faster than sound. So when the fire cracker burst Boojho saw the light before the sound of the cracker.

Question no – (14)

Answer :

Yes, when we hear a sound a thin stretched membrane called Ear Drum in our ear vibrates sending signal to inner ear.

Question no – (15)

Answer :

Sitar and Guitar are two musical instruments which produces sound by the vibration of strings.

Short Answer Questions :

Question no – (16)

Answer :

From the volume information we could conclude that,

Number of oscillation = 10

Time taken = 20s

Frequency = Number of oscillation / Time taken

= 10/20 = 0.5 Hz

So, time period of the pendulum

= 1/ frequency

= 1/0.5

= 2s

Question no – (17)

Answer :

We humans have a audible range of sound that is the sounds having frequencies between 20 – 20000 Hertz are only audible to us. Any sound outside that range are simply inaudible to us.

Question no – (18)

Answer :

The frying pan will vibrate but we would not be able to hear a sound as sound waves don’t travel in vacuum at all.

Question no – (19)

Answer :

Without any special device they wont be able to talk with each other because the sound don’t travel in vacuum, it needs a medium to travel from one place to other.

Question no – (20)

Answer :

The three sources of noise pollution in our area are –

• Honking of vehicles.

• Construction sounds.

• Loudspeakers.

Long Answer Questions :

Question no – (21)

Answer :

We know that the loudness of a sound depends on the amplitude of the sound wave. So when a string in the middle is plucked with a large force, it vibrates with a much larger amplitude and so produces a very loud sound.

Question no – (22)

Answer :

When a body vibrates by a force it creates a sound waves which travels by medium such as gas, liquid and solid. These waves are then picked up by our ears which has an ear drum that send this vibrations to the inner ears which is then processed by the brain after which we are able to hear a sound.

Question no – (23)

Answer :

The person is able to hear the alarm ring because the sound produced by it is travelling via the air present inside the glass veseel but when the air is being sucked out of the glass vessel, the person standing close to it will not be able to hear the sound that the alarm is producing.

Question no – (24)

Answer :

The sound of the clock appears much clearer at night because during night time there is not much other sounds travelling in the air. So the clock sound is facing least disturbance and produces a much clearer and audible sound.

Question no – (25)

Answer :

The three measures to limit noise pollution in our locality are :

• T.V and loudspeakers should be played at low volumes.

• Honking of vehicles should be minimized.

• Noise producing factories should be shifted to remote areas.

Other Chapter Solutions :

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👉 Microorganisms : Friend and Foe

👉 Synthetic Fibres and Plastics

👉 Materials : Metals and Non-Metals

👉 Coal and Petroleum