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Question: Answered & Verified by Expert
In YDSE, the slits have different widths. As a result, the amplitude of waves from two slits is A and 2A respectively. If I0 be the maximum intensity of the interference pattern then the intensity of the pattern at a point where the phase difference between waves is ϕ is given by I0P5+4cosϕ . Where P is in  integer. Find the value of P?
PhysicsWave OpticsJEE Main
Options:
  • A 9
  • B 3
  • C 6
  • D 1
Solution:
1602 Upvotes Verified Answer
The correct answer is: 9
As the amplitudes are A and 2A then the ratio of intensities is 1:4

Imax=I0=I1+I2+2I1×I2=I+4I+2×2I

I0=9II=I09

Intensity at any point:

I'=I1+I2+2I1×I2cosϕ

I'=I+4I+2I×4Icosϕ

I'=5I+4Icosϕ ; I'=I5+4cosϕ

I'=I095+4cosϕ=I0P5+4cosϕ

P=9

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