JEE MAIN - Physics (2022 - 25th June Morning Shift - No. 13)
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 P and Q will be :
2 I
6 I
5 I
7 I
Explanation
$${I_P} = I + 9I + 2\sqrt {I \times 9I} \cos {\pi \over 2} = 10I$$
$${I_Q} = I + 9I + 2\sqrt {I \times 9I} \cos \pi = 4I$$
So, $${I_P} - {I_Q} = 6I$$
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