Question

A wave source produces $20$ crests and $20$ troughs in $0.2sec$. 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

One complete wave consists of 1 crest and 1 trough.
Number of waves = $20$

Time taken = $0.2sec$

Frequency is the number of waves completed in 1 sec.

In 0.2 sec, number of waves = $20$

$\therefore$ In 1 sec, number of waves = $\frac{20}{0.2}$ = $100Hz$