Two sources `S_(1) and S_(2)` of sound having frequencies 338, 342 Hz are separated by a large distance. The speed of sound is 340 m/s. The velocity of the observer who is moving from `S_(2) " to " S_(1)` so that he does not hear any beats is

Options

A. 1 m/s
B. 2 m/s
C. 3 m/s
D. 4 m/s

Answer

B

Explanation

`n_(1) = ((v + v_(0))/(v)) n and n_(2) = n' [(v - v_(0))/(v)]`
`n_(1) = n_(2)`
`n [(v + v_(0))/(v)] = n' [(v - v_(0))/(v)]`
`v[n - n'] = -v_(0) [n + n']`
`v_(0) = [(n' - n)/(n + n')] v`
`= [(342 - 338)/(342 + 338)] xx 340`
`= (4 xx 340)/(680) = 2m//s`