Question

In a single slit diffraction of light of wavelength $\lambda$ by a slit of width $e$, the size of the central maximum on a screen at a distance $b$ is :

• A. $2b\lambda +e$
• B. $\frac{2b\lambda }{e}$
• C. $\frac{2b\lambda }{e}+e$
• D. $\frac{2b\lambda }{e}-e$

Answer 1

The correct option is C $\frac{2b\lambda }{e}+e$

Direction in which the first minima occurs is $\theta$.

$e\sin \theta =\lambda$

$\Rightarrow e\theta =\lambda$

$\theta =\frac{\lambda }{e}$ $(\sin \theta =\theta$, for small $\theta )$

Width of central maximum$=2b\theta +e=\frac{2b\lambda }{e}+e$.