Question

A parallel beam of monochromatic light of wavelength 5000 •Å is incident normally on a single narrow slit of width 0.001 mm. The light is focused by convex lens on screen, placed on its focal plane. The first minima will be formed for the angle of diffraction of ________ (degree).

Answer 1

For the first minima in a single-slit diffraction pattern:

$a \sin \theta = \lambda$

Given:
- $a = 0.001 \, \text{mm} = 1 \times 10^{-6} \, \text{m}$,
- $\lambda = 5000 \, \text{Å} = 5000 \times 10^{-10} \, \text{m}$.

Substituting:

$\sin \theta = \frac{\lambda}{a} = \frac{5000 \times 10^{-10}}{1 \times 10^{-6}} = 0.5$

$\theta = \sin^{-1}(0.5) = 30^\circ$
The Correct answer is: 30