When an object vibrates, it vibrates the neighbouring particles of the medium. These vibrating particles then vibrate to the adjacent particles In this way, vibrations produced by an object are transferred from one particle to another till it reaches to our ear.
Page 163 Explain how sound is produced by your school bell.
Ans: When the bell moves backwards, it creates a region of low pressure know as rarefaction. As the bell continues to move forward and backward, it creates a series of compressions and rarefactions. This produce the sound of a bell
Why sound waves are called mechanical waves?
Ans: Sound waves need the material medium to vibrate and propagate. Hence, these waves are known as mechanical waves. Sound waves propagate through a medium because of the interaction of the particles present in that medium.
Suppose you and your friend are on the moon. Will you be able to hear any sound produced by your friend?
Sound needs a medium to propagate. Since there is no material medium on the moon due to absence of atmosphere, you cannot hear any sound on the moon.
Page 166 Which wave property determines (a) loudness, (b) pitch?
(a) Amplitude of sound wave determines the loudness of a sound. The amplitude of a sound directly proportional to amplitude of wave. If the amplitude of a sound is large, then the sound produced will also be loud.
(b) Frequency of sound wave determines the pitch of a sound. The pitch of a sound is proportional to its frequency. High pitched sounds have high frequency
Guess which sound has a higher pitch: guitar or car horn?
The frequency of the vibration of a sound produced by a guitar is greater than that produced by a car horn. As we know that the pitch of a sound is directly proportional to its frequency, the guitar has a higher pitch than a car horn.
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