Question

An observer moves towards a stationary source of sound with one-fifth of the speed of sound. The wavelength and frequency of the source omitted are $\lambda$ and $f$ respectively. The apparent frequency and wavelength recorded by the observer are

• A. $0.85f,0.8\lambda$
• B. $1.2f,1.2\lambda$
• C. $1.2f,\lambda$
• D. $f,1.2\lambda$

Answer 1

The correct option is C $1.2f,\lambda$

$f_{app}=\frac{v+v/5}{v}f=1.2f$ ; wavelength remains unchanged.