A source of sound S is travelling at `(100)/(3)(m)/(s)` along a road, towards a point A. When the source is 3 m away from A, a person standint at a point O on a road perpendicular to AS hears a sound of requency `v'`. The distance of O from A at that time is 4 m. If the original frequency is 640 Hz, then the value of `v'` is (velocity of sound is `340(m)/(s)`)

Options

A. `620Hz`
B. `680Hz`
C. `720Hz`
D. `840Hz`

Answer

B

Explanation

`n.=n((V)/(V-V_(S)costheta))=640((340)/(340-(100)/(3)xx(3)/(5)))=680`