Optics Question 251

Question: A star moves away from earth at speed 0.8 c while emitting light of frequency $ 6\times 10^{14}Hz $ . What frequency will be observed on the earth (in units of 1014 Hz) (c = speed of light)

[MP PMT 1995]

Options:

A) 0.24

B) 1.2

C) 30

D) 3.3

Show Answer

Answer:

Correct Answer: B

Solution:

Observed frequency $ \nu ‘=\nu ( 1-\frac{v}{c} ) $

$ \Rightarrow \nu ‘=6\times 10^{14}( 1-\frac{0.8\ c}{c} )=1.2\times 10^{14}Hz $



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