Two persons `A` and `B` , each carring a source of frequency `300 H_(Z)` , are standing a few metre apart. A starts moving towards `B` with velocity `30 m//s` . If speed of sound is `300 m//s` , which of the following is true?

Options

A. (a) Number of beats heard by `A` is heigher than that heard by `B`
B. (b) The number of beats heard by `B` are `30 H_(Z)`
C. Both (a) and (b) are correct
D. Both (a) and (b) are wrong

Answer

D

Explanation

`(f_(b))A = f_(B) - f_(A)`
= `300((300 + 30)/(300)) - 300 = 30H_(Z)`
`(f_(b))B = f_(A) - f_(B)`
= `300 ((300)/(300 - 30)) - 300 = 33.33 H_(Z)`