Question

The figure shows Fraunhoffer's diffraction due to a single slit. If first minimum is obtained in the direction shown, then the path difference between rays $1$ and $3$ is

• A. $0$
• B. $\lambda /4$
• C. $\lambda /2$
• D. $\lambda$

Answer 1

Answer: (C)

In Fraunhoffer diffraction, for minimum intensity, $\Delta x=m\frac{\lambda }{2}$
For first minimum, $m=1\therefore \Delta x=\frac{\lambda }{2}$