Question

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

• A. $100\text{Hz}$
• B. $150\text{Hz}$
• C. $200\text{Hz}$
• D. $250\text{Hz}$

Answer 1

The correct option is A $100\text{Hz}$

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
$\frac{20}{0.2}=100$
So, the frequency is $100\text{Hz}$.