A bat moving at $10\,ms^{-1}$ towards a wall sends a sound signal of $8000\,Hz$ towards it. On reflection it hears a sound of frequency $f$. The value of $f$ in $Hz$ is close to (speed of sound $= 320\,ms^{-1}$ )
JEE MAIN 2015, Medium
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Reflected frequency of sound reaching bat
$ = \left[ {\frac{{V - \left( {{V_0}} \right)}}{{V - {V_s}}}} \right]f = \left[ {\frac{{V + {V_0}}}{{V - {V_s}}}} \right]f = \frac{{V + 10}}{{V - 10}}f$
$ = \left( {\frac{{320 + 10}}{{320 - 10}}} \right) \times 8000 = 8516Hz$
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