An observer moves towards a stationary source of sound with a speed `((1)/(5))`th of the speed of sound. The wavelength and frequency of the source emitted are `lamda` and f, respectively. The apparent frequency and wavelength recorded by the observer are, respectively.

Options

A. `1.2f, 1.2 lambda`
B. `1.2f, lambda`
C. `f, 1.2 lambda`
D. `0.8f, 0.8 lambda`

Answer

B

Explanation

Apparent frequency, `f.=(v+v_(0))/(v)f`
`rArr f.=(v+(1//5)v)/(v)f=1.2f`
Wavelength does not change by motion of observer.