Q. When two coherent monochromatic beams of intensity I and 9I interface, the possible maximum and minimum intensities of the resulting beam are
A) 9I and I
B) 9I and 4I
C) 16I and 4I
D) 16I and I
Explanation
(c) Given, $I_{1} = I$ and $I_{2} = 9I$
Maximum intensity $= \left( \sqrt{I_{1}} + \sqrt{I_{2}} \right)^{2}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \left( \sqrt{I} + \sqrt{9I} \right)^{2} = 16I$
Minimum intensity
$= \left( \sqrt{I_{1}} - \sqrt{I_{2}} \right)^{2} = \left( \sqrt{I} - \sqrt{9I} \right)^{2} = 4I$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.