Wave Mechanics Question 691

Question: An observer moves towards a stationary source of sound with a speed 1/8th of the speed of sound. The wavelength and frequency of the sound emitted are $ \lambda $ and $ f $ respectively. The apparent frequency and wavelength recorded by the observer are respectively.

Options:

A) $ 0.4f,0.4\lambda $

B) $ 0.6f,1.6\lambda $

C) $ 1.4f,\lambda $

D) $ 1.1f,\lambda $

Show Answer

Answer:

Correct Answer: D

Solution:

[d] $ f _{apparent}=( \frac{u+u/5}{u} )f=\frac{6}{5}f=1.2f $ Wavelength remains constant (unchanged) in this case.