Optics Question 264

Question: The $ 6563{AA} $ line emitted by hydrogen atom in a star is found to be red shifted by $ 5{AA} $ . The speed with which the star is receding from the earth is

[Pb. PMT 2002]

Options:

A) 17.29 - 109 m/s

B) 4.29 - 107 m/s

C) 3.39 - 105 m/s

D) 2.29 - 105 m/s

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Answer:

Correct Answer: D

Solution:

$ \frac{\Delta \lambda }{\lambda }=\frac{v}{c}\Rightarrow v=\frac{\Delta \lambda }{\lambda }.c $

$ =\frac{5}{6563}\times (3\times 10^{8})=2.29\times 10^{5} $ m/sec



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