When the observer moves towards the stationary source with velocity, `v_1`, the apparent frequency of emitted note is `f_1`. When the observer moves away from the source with velocity `v_1`, the apparent frequency is `f_2`. If v is the velocity of sound in air and `f_1/f_2` = 2,then `v/v_1` = ?

Options

A. 2
B. 3
C. 4
D. 5

Answer

B

Explanation

`F_(1) = ((v + v_(1))/(v))f` where f is the real frequency
and `F_(2) = ((v - v_(f))/(v)) f`
`:. (F_(1))/(F_(2)) = (2)/(1) = (v + v_(1))/(v - v_(1))`
`:. 2v - 2v_(1) = v + v_(1) " " :. v = 3v_(1)`
`:. (v)/(v_(1)) = 3`