Optics Question 257

Question: A star is moving towards the earth with a speed of $ 4.5\times 10^{6} $ m/s. If the true wavelength of a certain line in the spectrum received from the star is $ 5890{AA} $ , its apparent wavelength will be about $

[c=3\times 10^{8}m/s] $ [MP PMT 1999]

Options:

A) $ 5890{AA} $

B) $ 5978{AA} $

C) $ 5802{AA} $

D) $ 5896{AA} $

Show Answer

Answer:

Correct Answer: C

Solution:

$ \lambda ‘=\lambda ( 1-\frac{v}{c} )=5890( 1-\frac{4.5\times 10^{6}}{3\times 10^{8}} ) $

$ \approx 5802{AA} $



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