If vibrating tuning fork of frequency 255Hz is moving with a velocity `4ms^-1` towards the wall the number of beats heard per second is (speed of sound in air = `340ms^-1`).

Options

A. 3
B. 4
C. 5
D. 6

Answer

A

Explanation

Apparent frequency ,`n'=n(v/(v-v_s))`
`v=340ms^-1` and `v_s=4ms^-1` ,n = 255
`implies n'=255xx(340/(340-4))`
`implies n'= 258 "Hz"`
Number of beats heard =258-255=3