A) 2150 Hz
B) 2500 Hz
C) 1800 Hz
D) 2400 Hz
Correct Answer: B
Solution :
Given \[{{f}_{A}}=1800Hz\] \[{{v}_{t}}=v\] \[{{f}_{B}}=2150Hz\] Reflected wave frequency received by A, \[{{f}_{A}}'=?\] Applying doppler?s effect of sound, \[f'=\frac{{{v}_{s}}f}{{{v}_{s}}-{{v}_{t}}}\]here, \[{{v}_{t}}={{v}_{s}}\left( 1-\frac{{{f}_{A}}}{{{f}_{B}}} \right)\] \[=343\left( 1-\frac{1800}{2150} \right)\]\[{{v}_{t}}=55.8372m/s\] Now, for the reflected wave, \[\therefore \]\[f_{A}^{'}=\left( \frac{{{v}_{s}}+{{v}_{t}}}{{{v}_{s}}-{{v}_{t}}} \right){{f}_{A}}\]\[=\left( \frac{343+55.83}{343-55.83} \right)\times 1800\] \[=2499.44\approx 2500Hz\]You need to login to perform this action.
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