Question

A source of wave produces 20 troughs n 20 crests in 0.2s. Find the frequency of the wave

Answer 1

1 crest and 1 trough complete 1 wave. So, 20 crests and 20 troughs complete 20 waves.

In 0.2 s we have 20 complete waves

So, in 1 s we have, f = 20/0.2 = 100 Hz. This is the frequency.

So the frequency is 100Hz.