A stationary sound source S of frequency 334 | vedclass

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(D) The problem involves two steps of the Doppler effect.Step $1$: The reflecting surface acts as an observer moving away from the source $S$. The fre

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$330$

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(D) The problem involves two steps of the Doppler effect.Step $1$: The reflecting surface acts as an observer moving away from the source $S$. The frequency $f'$ received by the surface is given by $f' = f \left( \frac{V - u}{V} ight)$,where $f = 334 \, Hz$,$V = 330 \, m/s$,and $u = 2 \, m/s$.$f' = 334 \left( \frac{330 - 2}{330} ight) = 334 \left( \frac{328}{330} ight) \approx 331.97 \, Hz$.Step $2$: The reflecting surface now acts as a moving source reflecting the sound back to the stationary observer $O$. The frequency $f''$ heard by the observer is $f'' = f' \left( \frac{V}{V + u} ight)$.$f'' = 334 \left( \frac{328}{330} ight) 	imes \left( \frac{330}{330 + 2} ight) = 334 \left( \frac{328}{332} ight) = 334 	imes 0.98795 \approx 330 \, Hz$.

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