Question

An observer moves towards a stationary source of sound, with a velocity one-fifth of the velocity of sound. What is the percentage increase in the apparent frequency?
A. `5%`
B. `20%`
C. `0%`
D. `0.5%`

Answer 1

Correct Answer - B
`f=f_0((v_S+v_0)/(v_S))`
`=f_0[(v+(v)/(5))/(v)]`
`=(6)/(5)f_0`
Hence, percentage increase is
`[((6)/(5)f_0-f_0)/(f_0)]xx100=20%`