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} $
