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An observer moves towards a stationary source of sound with a speed 1/5th of the speed of sound. The wavelength and frequency of the source emitted are $\lambda$ and $f$ respectively. The apparent frequency and wavelength recorded by the observer are respectively:
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Verified Answer
The correct answer is:
$1.2 f, \lambda$
Source is stationary
$$
\begin{aligned}
& \Rightarrow \lambda=\text { constants } \\
& \text { and } f^{\prime}=\frac{V+V_{\mathrm{s}}}{V} f=\left(1+\frac{V_{\mathrm{s}}}{V}\right) f \\
& =\left(1+\frac{1}{5}\right) f=1.2 f
\end{aligned}
$$
$$
\begin{aligned}
& \Rightarrow \lambda=\text { constants } \\
& \text { and } f^{\prime}=\frac{V+V_{\mathrm{s}}}{V} f=\left(1+\frac{V_{\mathrm{s}}}{V}\right) f \\
& =\left(1+\frac{1}{5}\right) f=1.2 f
\end{aligned}
$$
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