question_answer

An observer is moving with half the speed of light towards a stationary microwave source emitting waves at frequency 10 GHz. What is the frequency of the microwave measured by the observer?[JEE Main 2017] (speed of light\[=3\times {{10}^{8}}\,m{{s}^{-1}}\])

A) 17.3 GHz

B) 15.3 GHz

C) 10.1 GHz

D) 12.1 GHz

Correct Answer: A

Solution :

[a] Doppler effect in light (speed of observer is not very small compare to speed of light)