In the figure shown a source of sound of frequency `510 Hz` moves with constant velocity `v_(S) = 20 m//s` in the direction shown. The wind is blowing at a constant velocity `v_(W) = 20 m//s` towards an observer who is at rest at point `B`. The frequency detected by the observer by corresponding to the sound emitted by this source at initial position `A`, will be (speed of sound relative to air `= 330 m//s`).

Options

A. `485 Hz`
B. `500 Hz`
C. `512 Hz`
D. `525 Hz`

Answer

B

Explanation

Apparent frequency
`n' n = ((u + v_(W)))/((u + v_(W) - v_(S) cos 60^(@))) = (510(330 + 20))/(330 + 20 - 20 cos 60^(@)) = 510 xx (350)/(340) = 525 Hz`