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The two light beams having intensities I and 9I interfere to produce a fringe pattern on a screen. The phase difference between the beams is \pi / 2 at point P and \pi at point Q. Then the difference between the resultant intensities at \mathrm{P} and \mathrm{Q} will be :

Option: 1

2I


Option: 2

6I


Option: 3

5I


Option: 4

7I


Answers (1)

best_answer


\mathrm{I_{P}= I_{1}+I_{2}+2\sqrt{I_{1}}\sqrt{I_{2}}\cos \left ( \frac{\pi}{2} \right )}
\mathrm{I_{P}= 10\, I\: \rightarrow (1)}

\mathrm{I_{Q}= I+9I+2\sqrt{I}\sqrt{9I}\cos \left ( \pi \right )}
\mathrm{I_{Q}= 4I\: \rightarrow (2)}

\mathrm{I_{P}-I_{Q}= 6I}

The correct option is (2)

Posted by

Sanket Gandhi

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