A whistling engine is approaching a stationary observer with velocity 110 m/s. The velocity of sound is 330 m/s. The ratio of frequencies as heard by observer at the time of approaching and passing of engine is :

Options

A. `4 : 3`
B. `3: 6 `
C. `4: 1`
D. `2 : 1`

Answer

D

Explanation

`v_(1) ((V)/(V - U_(s))) v and v_(2) = ((V)/(V + U_(s)))` V
`therefore (v_(1))/(v_(2)) = (V + U_(s))/(V - U_(s)) = (330 + 110)/(330 - 110) = (v_(1))/(v_(2)) = 2 `
Hence the correct choice is (d).