Lakhmir singh solutions science class 8 Solutions for Chapter 13 sound

Exercises in Chapter 13 sound Grade 8

Exercise

Questions in Exercise

How is the sound produced?

What should an object do to produce sound?

How does a sound-making object differ from one that is silent?

Name the part which vibrates to produce sound in the following:

(a) Drums

(b) Sitar

What brings the sound of a ringing telephone bell to our ears?

What is the length of vocal cords in a man?

What is a spring balance?

Out of a man and a woman:

(a) who has shorter vocal cords?

(b) who produces a sound of a higher pitch?

Give any four sources of sound in a market place.

Name the sound-producing organ in humans.

Which part of our body vibrates when we speak?

What does the working of a toy telephone tell us about sound?

Name one solid, one liquid and one gas through which sound can travel.

Which of the following cannot transmit sound?

Is the speed of sound more in water or steel?

Where would sound travel faster-in wood or in the water?

In which medium sound travels faster: air or iron?

In which medium sound travels fastest: air, water or steel?

Out of solids, liquids and gases:

(a) in which medium sound travels slowest?

(b) in which medium sound travels fastest?

What is the speed of sound in air?

Which of the following is the speed of sound in water and which in steel?

(a) 5000 m/s

(b) 1500 m/s

Name the organs of hearing in our body.

Name that part of the ear which vibrates when outside sound falls on it.

Name the three tiny bones present in the middle part of the ear.

What is the function of three tiny bones in the ear?

Name the nerve which carries electrical impulses from the cochlea of the ear to the brain.

What is the name of passage in the outer ear which carries sound waves to the eardrum?

Name the quantity whose unit is 'hertz'.

What is the relation between 'time-period' and 'frequency' of an oscillating body?

Name three characteristics which are used to describe oscillations (or vibrations).

What is the scientific name for the following?

The number of vibrations made per second.

What name is given to the maximum displacement of a vibrating body from its central position?

If 125 oscillations are produced in 5 seconds, what is the frequency in hertz?

How does loudness depend on the amplitude of vibrations?

By how much will the loudness of a sound change when the amplitude of vibrations is:

(a) doubled?

(b) halved?

Name the unit used to measure the loudness of sound. Also, write its symbol.

What is the loudness of a normal conversation in decibels?

On what factor does the pitch of a sound depend?

How is pitch related to frequency?

Name the characteristic of sound which enables us to distinguish between a man's voice and a woman's voice even without seeing them.

Arrange the following sounds in the order of increasing frequencies (keeping the sound of the lowest frequency first):

(i) Baby's voice

(ii) Man's voice

(iii) Woman's voice

Which produces the sound of a higher pitch: a drum or a whistle?

Name the characteristic of sound which depends on:

(a) Amplitude.

(b) Frequency.

Name the characteristic of sound which can distinguish between the 'notes' (musical sounds) played on a flute and a sitar (both the notes having the same pitch and loudness).

Write the full form of dB.

What is the name of very high-frequency sounds which cannot be heard by the human ear?

Why do we not hear the screams of a bat?

Which of the following frequency of sound can be heard by a dog but not by a man?

(a) 50,000 hertz.

(b)15,000 hertz.

Name the substance which vibrates in a flute to produce sound.

State whether the following statements are true or false:

(a) Sound cannot travel in a vacuum.

(b) The number of oscillations per second of a vibrating object is called its time period.

(d) The lower the frequency of vibration, the higher is the pitch.

(e) If the amplitude of vibrations is doubled, the loudness of sound also gets doubled.

(f) When the amplitude of vibrations is halved, the loudness of sound becomes one-fourth.

(g) Unwanted or unpleasant sound is termed as music.

(h) Noise pollution may cause partial hearing impairment.

Fill in the following blanks with suitable words:

(a) Sounds are produced by ________ objects.

(b) The human voice box is called ________

(d) A set of three tiny ________ in the middle part of ear passes on sound vibrations from the eardrum to the liquid in the cochlea.

(e) The unit of frequency is ________

(f) The time taken by an object to complete one oscillation is called ________

(g) The shrillness of a sound is determined by the ________ of vibration.

(h) Unpleasant sound is called ________

(i) Sound which is pleasing to the ear is called ________ sound.

(j) A person having partial hearing loss can hear properly by wearing a device called the hearing ________ on the ear.

(a) What is the name of the strings in the human voice box which vibrate to produce sound?

(b) What makes these strings vibrate?

Describe how sound is produced by the human voice box (or larynx).

What is the frequency of the sound produced when the vocal cords are:

(a) tight and thin?

(b) loose and thick?

Why are the voices of men, women and children different?

If you want to hear a train approaching from far away, why is it more convenient to put the ear to the track?

State one observation from everyday life which shows that sound travels much slower than light.

Explain why the flash of lightning is seen first but the sound of thunder is heard a little later (though lightning and thunder take place in the sky at the same time and the same distance from us).

Name the object (or part) which vibrates to produce sound in the following musical instruments:

(a) Sitar

(b) Dholak

(d) Cymbals

(e) Veena

(f) Tabla

Name one musical instrument each in which the sound is produced:

(a) By vibrating a stretched string.

(b) By vibrating air enclosed in a tube.

(d) By vibrating metal plates.

Give two examples of each of the following:

(a) Stringed musical instruments.