Optics Question 241
Question: A spectral line $ \lambda =5000{AA} $ in the light coming from a distant star is observed as a $ 5200{AA} $ . What will be recession velocity of the star
Options:
A) $ 1.15\times 10^{7}cm/\sec $
B) $ 1.15\times 10^{7}m/\sec $
C) $ 1.15\times 10^{7}km/\sec $
D) 1.15 km/sec
Show Answer
Answer:
Correct Answer: B
Solution:
$ \Delta \lambda =5200-5000=200{AA} $ Now $ \frac{\Delta \lambda }{\lambda ‘}=\frac{v}{c}\Rightarrow v=\frac{c\Delta \lambda }{\lambda ‘}=\frac{3\times 10^{8}\times 200}{5000} $
$ =1.2\times 10^{7}m/\sec \approx 1.15\times 10^{7}m/\sec $
