Worksheet solutions for chapter: Sound for class 8 are provided below.
(1) What are the maximum and minimum limits of human’s ear to hear?
The maximum hearing limit of human’s ear = 20,000Hz
The minimum hearing limit of human’s ear = 20Hz
(2) What are the differences between the loudness and pitch of the sound?
The differences between the loudness and pitch are tabulated below:-
|It depends on the amplitude of the sound.||It depends on the frequency of pitch.|
|If amplitude of the sound is high the loudness of sound is also high and vice versa.||If frequency of sound vibration is high the pitch of sound is also high and vice versa.|
|It is measured in unit decibel (db).||It is measured in unit Hertz(Hz).|
(3) What is sound?
Sound is a vibration (wave) produced by a vibrating body through the air or other medium.
Eg:- (i) Touch school bell when producing sound, you will feel vibration.
(ii) Tie rubber band from both ends and vibrate them, you will hear a sound.
(4) Show how can sound travel in water?
Sound can travel in water.
Fill a tub with water. Shake a bell inside the tub. Now put your ear at the surface of water and listen the sound of bell. Therefore, sound can travel in water.
(5) An object oscillates 50 times in 10 seconds. Find the frequency of the object.
Number of oscillations of pendulum = 50
Time taken in 50 oscillations = 10 sec
Frequency of pendulum = Number of oscillations/Time taken
= 50/ 10
= 5 Hz
Hence, frequency of pendulum is 5Hz.
(6) Match the items in column A with the items column B
Column A Column B
(a) Frequency hearing impairment
(b) 10,000Hz inaudible sounds
(c) Sound cannot travel Hz
(d)10Hz audible sound
Column A Column B
(i) Frequency hearing impairment (iii)
(ii) 10,000Hz inaudible sounds (iv)
(iii) Noise Hz (i)
(iv))10Hz audible sound (ii)
(7) Select the given items under “Low frequency” and High frequency”.
Voice of woman, voice of guitar, voice of lion, voice of crackers, voice of cow and voice of iron sheet
|High frequency||Low frequency|
|Voice of woman||Voice of lion|
|Voice of guitar||Voice of cow|
|Voice of cracker|
|Voice of iron sheet|
(8) Which part of our body vibrates when we speak?
Voice box of our body vibrates when we speak. It is at the upper end of the windpipe.
(9) How dolphins communicate under water?
Sound waves can travel in water. Therefore, dolphins can communicate under water.
(10) What are the differences between audible and inaudible sounds?
The difference between audible and inaudible sounds are tabulated below:-
|Audible Sound||Inaudible Sound|
|The frequencies of sound which humans can hear.||The frequencies of sound which humans cannot hear.|
|The range of audible frequencies of human ear is approximately from 20 to 20,000 Hz.||The range of inaudible frequencies of human ear is less than 20 Hz and higher than 20,000 Hz.|
|Eg:- Music, normal talk, Voice of television etc.|