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?

Options

A. `5%`
B. `20%`
C. zero
D. `0.5%`

Answer

B

Explanation

When observer moves towards stationary source then apparent frequency
`n'=[(v+v_O)/(v)]n=[(v+(v)/(5))/(v)]n=(6)/(5)n=1.2n`
Increment in frequency `=0.2n` so percentage change
In frequency `=(0.2n)/(n)xx100=20%`