Q. In an interference pattern by two identical slits, the intensity of central maxima is $I$. what will be the intensity of the same spot, if one of the slits is closed?
A) $I/4\ $
B) $I/2$
C) $I$
D) $2I$
Explanation
(a) $I_{R} = I_{1} + I_{2} + 2\sqrt{I_{1}I_{2}}\cos\phi$
$I_{0} = I + I + I + 2I\cos{0{^\circ} = 4I}$
When one of the slits is closed, intensity on the same spot
$= I = I_{0}/4$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.