Physics - Sound Wave Question with Solution | TestHub

Let $v$ be the velocity of sound and $n$ be the actual frequency of the source.

Velocity of the observer, $v_o=\frac{v}{5}$

Velocity of the source, $v_s=0$

Apparent frequency $n^{\prime }$ is given by:

$n^{\prime }=n\left(\frac{v+v_o}{v}\right)$

$n^{\prime }=n\left(\frac{v+\frac{v}{5}}{v}\right)=n\left(1+\frac{1}{5}\right)=\frac{6}{5}n$

Percentage increase in apparent frequency is:

$\frac{n^{\prime }-n}{n}\times 100=\frac{\frac{6}{5}n-n}{n}\times 100=\frac{1}{5}\times 100=20\%$

Answer: $20\%$