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Question: Answered & Verified by Expert
Interference fringes are produced on a screen by using two light sources of intensities I and 9I. The phase difference between the beams is π2 at the point P and π at the point Q on the screen. The difference between the resultant intensities at point P and Q is
PhysicsWaves and SoundMHT CETMHT CET 2016
Options:
  • A 2I
  • B 4I
  • C 6I
  • D 8I
Solution:
2694 Upvotes Verified Answer
The correct answer is: 6I
At point P, resultant intensity of interfering wave is
IPres=I1+I2+2I1I2cos θ
For θ=π2,IPres=I+9I=10I
At point Q, resultant intensity of interfering wave is
IQres=10I-2.9I2=10I-6I=4I for θ=π
  I=IPres-Igres=10I-10I+6I=6I

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