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