Question

A sound of wave produces $40$ crests and $40$ troughs in $0.4s$. What is the frequency of the wave?

• A. $10Hz$
• B. $50Hz$
• C. $100Hz$
• D. $150Hz$

Answer 1

Answer: (C)

$100Hz$

One complete cycle consists of one crest and one trough.
The given source produces 40 crests and 40 troughs, hence it produces 40 wave cycles in the given interval 0.4 seconds.

Therefore, number of wave cycles produced in 1 second $=\frac{40\times 1}{0.4}=100$

We know that the number of wave cycles produced in one second is equal to the frequency.

Hence, the frequency of the wave is 100 Hz.