Question

A wave source produces $20$ crests and $20$ troughs in $0.2$ sec. Find the frequency of the wave.

• A. 200 Hz
• B. 500 Hz
• C. 100 Hz
• D. 300 Hz

Answer 1

The correct option is C

100 Hz

A crest is the maximum value of the wave quantity. So at the source, the wave quantity attains maximum value for $20$ times in $0.2$ sec. The number of times it becomes maximum in $1$ second is $\frac{20}{0.2}=100$.