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Question: Answered & Verified by Expert
Two coherent sources of intensities $\mathrm{l}_{1}$ and $\mathrm{I}_{2}$ produce an interference pattern on screen. The maximum intensity in the interference pattern is
PhysicsWave OpticsJEE Main
Options:
  • A $\left[\sqrt{\mathrm{I}_{1}}+\sqrt{\mathrm{I}_{2}}\right]^{2}$
  • B $\mathrm{I}_{1}+\mathrm{I}_{2}$
  • C $\left(\mathrm{I}_{1}+\mathrm{I}_{2}\right)^{2}$
  • D $\mathrm{I}_{1}^{2}+\mathrm{I}_{2}^{2}$
Solution:
1011 Upvotes Verified Answer
The correct answer is: $\left[\sqrt{\mathrm{I}_{1}}+\sqrt{\mathrm{I}_{2}}\right]^{2}$
Intensity is proportional to square of the amplitude.
$\mathrm{I} \propto \mathrm{a}^{2}$
$\therefore \sqrt{\mathrm{I}} \propto \mathrm{a}$
Maximum intensity is produced when the two amplitudes get added (phase difference is $2 n \pi$ ).
$\therefore \mathrm{I}_{\max } \propto\left(\mathrm{a}_{1}+\mathrm{a}_{2}\right)^{2} \quad$ or $\mathrm{I}_{\max } \propto\left(\sqrt{\mathrm{I}}_{1}+\sqrt{\mathrm{I}}_{2}\right)^{2}$

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