Two source of sound S1 and S2 produce sound waves of same frequency 660 Hz. A listener is moving from source S1 towards S2 with a constant speed um/s and he hears 10 beat/s. Then, u is equal to ________ (in m/s).

Options

A. 5.5m/s
B. 15.0m/s
C. 10.0m/s
D. 2.5m/s

Answer

D

Explanation

`f_(1) = f_(0)((v-u)/(v))` and `f_(2) = f_(0)((v + u)/(v)) , f_(2)-f_(1) = (f_(0))/(v) 2 u` `rArr u = (v(f_(2)- f_(1)))/(2f_(0))` = `(330 xx 10)/(2 xx 660) = 2.5 m//s`