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. corresponding to the sound emitted by the source at initial position A, the frequency detected by the observer is equal to (speed of sound relative to air is `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`