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Question: Answered & Verified by Expert
Two coherent sources of intensities, $l_1$ and $I_2$ produce an interference pattern. The maximum intensity in the interference pattern will be
PhysicsWave OpticsJEE Main
Options:
  • A $l_1+I_2$
  • B $I_1^2+I_2^2$
  • C $\left(I_1+I_2\right)^2$
  • D $\left(\sqrt{I_1}+\sqrt{I_2}\right)^2$
Solution:
2592 Upvotes Verified Answer
The correct answer is: $\left(\sqrt{I_1}+\sqrt{I_2}\right)^2$
Resultant intensity $I_R=I_1+I_2+2 \sqrt{I_1 I_2} \cos \phi$
For maximum $I_R, \quad \phi=0^{\circ}$
$\Rightarrow I_R=I_1+I_2+2 \sqrt{I_1 I_2}=\left(\sqrt{I_1}+\sqrt{I_2}\right)^2$

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