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Chapter -13, , Sound, , Exercise Page No 168:, , Question 1:, , Choose the correct answer., , Sound can travel through, , (a) gases only (b) solids only, , (c) liquids only (d) solids, liquids and gases., , Answer:, , (d) Sound can travel through solids, liquids, and gases.

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Question 2:, , Which of the following voices is likely to have minimum frequency?, (a) Baby girl (b) Baby boy, , (c) Aman (d) A woman, , Answer:, , (c) Aman

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Question 4:, Fill in the blanks with suitable words., , (a) Time taken by an object to complete one oscillation is called, , (b) Loudness is determined by the_____ of vibration., , (c) The unit of frequency is, , (d) Unwanted sound is called, , (e) Shrillness of a sound is determined by the _____ of vibration., , Answer:, , (a) Time taken by an object to complete one oscillation is called _time, period__., , , , (b) Loudness is determined by the__amplitude_ of vibration., , (c) The unit of frequency is __hertz (Hz) __., , (d) Unwanted sound is called __noise_., , (e) Shrillness of a sound is determined by the _frequency__ of vibration., , (Shrillness is also called pitch of the sound. Pitch is directly proportional, to the frequency of vibration. Hence, shrillness is determined by the, frequency of vibration.)

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Question 5:, A pendulum oscillates 40 times in 4 seconds. Find its time period and, frequency., , Answer:, , Frequency of oscillations is defined as the number of oscillations of a, vibrating body per second. It is given by, , . Number of oscillations 49, Frequency= —————_———— - *" ~|0 Hz, Total time, , The time required to complete one oscillation is known as time period. It, is given by the inverse of the frequency., , I 1, - =—=0.1s, Time period Frequency of oscillation 10

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Question 6:, , The sound from a mosquito is produced when it vibrates its wings at an, average rate of 500 vibrations per second. What is the time period of, the vibration?, , Answer:, , The time required to complete one oscillation is known as time period. It, is given by the inverse of the frequency., , l, Time period - Frequency of oscillation, , Frequency of oscillations = 500 Hz, , = | =0,002 s, Time period 500