Optics Question 1039
Question: Two beams of light having intensities I and 4I interfere to produce a fringe pattern on a screen. The phase difference between the beams is $ \frac{\pi }{2} $ at point A and p at point B. Then the difference between the resultant intensities at A and B is
[IIT JEE (Screening) 2001]
Options:
A) 2I
B) 4I
C) 5I
D) 7I
Show Answer
Answer:
Correct Answer: B
Solution:
At point A, resultant intensity $ I _{A}=I _{1}+I _{2}=5I; $
and at point B $ I _{B}=I _{1}+I _{2}+2\sqrt{I _{1}I _{2}}\cos \pi =5I+4I $
$ I _{B}=9I $ so $ I _{B}-I _{A}=4I. $
