question_answer

A bat moving at \[10m{{s}^{-1}}\] towards a wall sends a sound signal of ROOO Hz towards it. On reflection it hears a sound of frequency f. The value of f in Hz is dose to (speed of sound \[=320m{{s}^{-1}}\]) JEE Main Online Paper (Held On 10 April 2015)

A)  8516

B)  8000

C)   8424

D)  8258

Correct Answer: A

Solution :

                 \[f'=\left( \frac{320+10}{320-10} \right)\times 8000\] \[=\frac{330}{310}\times 8000\]                                \[=8516Hz\]