Q. Two coherent monochromatic light beams of intensities $I$ and $4I$ are superposed. The maximum and minimum possible intensities in the resulting beam are
A) $5I$ and $I$
B) $5I$ and $3I$
C) $9I$ and $I$
D) $9I$ and $3I$
Explanation
(c) $I_{\max} = \left( \sqrt{I_{1}} + \sqrt{I_{2}} \right)^{2} = \left( \sqrt{I} + \sqrt{4I} \right)^{2} = 9I$
$I_{\min} = \left( \sqrt{I_{1}} - \sqrt{I_{2}} \right)^{2} = \left( \sqrt{I} - \sqrt{4I} \right)^{2} = I$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.