Q. Consider Fraunhoffer diffraction pattern obtained with a single slit at normal incidence. At the angular position of first diffraction minimum, the phase difference between the wavelets from the opposite edges of the slit is
A) $\pi/4$
B) $\pi/2$
C) $\pi$
D) $2\pi$
Explanation
(d) To have the first minimum, the path difference between the waves from $A$ and $B = BD = \frac{a}{2}.\sin\theta = \frac{\lambda}{2}$. The path difference between the waves from $A$ and $C$ at the same point should be $\lambda$ or phase difference is $2\pi$
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Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.