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 $
