Optics Question 250
Question: A star emitting light of wavelength $ 5896{AA} $ is moving away from the earth with a speed of 3600 km / sec. The wavelength of light observed on earth will
[MP PET 1995, 2002]
Options:
A) Decrease by $ 5825.25{AA} $
B) Increase by $ 5966.75{AA} $
C) Decrease by $ 70.75{AA} $
D) Increase by $ 70.75{AA} $ ( $ c=3\times 10^{8}m/\sec $ is the speed of light)
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Answer:
Correct Answer: D
Solution:
$ \Delta \lambda =\frac{\nu }{c}\lambda $
$ =\frac{3600\times 10^{3}}{3\times 10^{8}}\times 5896=70.75{AA} $ So the increased wavelength of light is observed.
