Question

a sound wave produce 20 crest and 20trough in 0.2sec find the frequency of wave

Answer 1

One oscillation = 1 crest & 1 trough
20 crest & 20 trough = 20 oscillation
Time = 0.2 sec
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Frequency = No. of oscillation/Time
= 20/0.2
= 200/2
= 100 Hz

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Answer 2

Solution :

Since the sound wave produces 20 crests in 0.2 second, the density of the medium at a place becomes maximum 20 times in 0.2 second. The number of times it becomes maximum in 1 second is

$\sf \frac{20}{0.2} \\ \\ \sf 10 \times 10 \\ \\ \sf 100$

So, the frequency is 100 times /second or 100 Hz.

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