Q. In Young’s double slit experiment the two slits are d distance apart. Interference pattern is observed on a screen at a distance D from the slits. A dark fringe is observed on the screen directly opposite to one of the slits. The wavelength of light is
A) $\frac{D^{2}}{2d}$
B) $\frac{d^{2}}{2D}$
C) $\frac{D^{2}}{d}$
D) $\frac{d^{2}}{D}$
Explanation
(d) $n$th dark fringe
$\ \ \ \ \ \ (2n - 1)\frac{D\lambda}{2d} = \frac{d}{2}$
$\lambda = \frac{d^{2}}{(2n - 1)D} = \frac{d^{2}}{D}$
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Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.