The speed of sound in air is 340 m/s. The speed with which a source of sound should move towards a stationary observer so that the apparent frequency becomes twice of the original

Options

A. 170 m/s
B. 340 m/s
C. 640 m/s
D. 85 m/s

Answer

A

Explanation

`n' = (V)/(V- V_(S)).n`
`2n = (V)/(V- V_(S)) n`
`:. 2V - 2V_(S) V :. V_(S) = (V)/(2)`
`:. V_(S) = (340)/(2) = 170 m//s`