Two coherent light beams of intensities \( I \) and \( 4I \) are superimposed to produce an interference pattern. The maximum and minimum intensities in the resultant interference pattern are
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \( 9I \) and \( I \)
For coherent beams the amplitudes add, and intensity is proportional to the square of the amplitude, so \( a \propto \sqrt{I} \).
\( \displaystyle I_{\max} = \left(\sqrt{I_1} + \sqrt{I_2}\right)^{2} = \left(\sqrt{I} + 2\sqrt{I}\right)^{2} = 9I \)
\( \displaystyle I_{\min} = \left(\sqrt{I_2} - \sqrt{I_1}\right)^{2} = \left(2\sqrt{I} - \sqrt{I}\right)^{2} = I \)
Note: The same question was also asked in CUET (UG) 2023 on 09-06-2023 (Slot 3) and on 22-05-2023 (Slot 3), and a similar question in CUET (UG) 2026 on 18-05-2026 (Slot 2).