An observer is approacing a stationary source with a velocity `1/4 th` of the velocity of sound. Then the ratio of the apparent frequency to actual frequency of source is

Options

A. a)`4:5`
B. b)`5:4`
C. c)`2:3`
D. d)`3:2`

Answer

B

Explanation

When an observer is moving towards the source apparent frequency
`n.= ntimes ((v_1+v_0)/v)`
or `n.=n times ((v+v//4)/v)`
or `n.=n times 5/4`
or `(n.)/n=5/4`