Physics - Sound Wave Question with Solution | TestHub

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

The velocity of the observer moving towards the stationary source is $v_o=\frac{v}{5}$.

According to the Doppler effect, the apparent frequency $f^{\prime }$ is given by:

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

Substituting the value of $v_o$:

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

The percentage increase in the apparent frequency is:

$\frac{f^{\prime }-f}{f}\times 100=\left(\frac{\frac{6}{5}f-f}{f}\right)\times 100$

$=\frac{1}{5}\times 100=20\%$

Answer: $20\%$