Physics - Sound Wave Question with Solution | TestHub

The car acts as a source moving towards a stationary observer (the wall) with speed $V_1$.

The apparent frequency received by the wall is $n^{\prime }=n\left(\frac{V}{V-V_1}\right)$.

The wall reflects this sound, acting as a stationary source of frequency $n^{\prime }$.

The driver acts as an observer moving towards the stationary source (the wall) with speed $V_1$.

The apparent frequency heard by the driver is $n^{\prime \prime }=n^{\prime }\left(\frac{V+V_1}{V}\right)$.

Substituting the value of $n^{\prime }$, we get:

$n^{\prime \prime }=n\left(\frac{V}{V-V_1}\right)\left(\frac{V+V_1}{V}\right)=n\left(\frac{V+V_1}{V-V_1}\right)$.

Answer: $\left(\frac{V+V_1}{V-V_1}\right)n$