Q. A parallel beam of light of wavelength 3141.59$\mathring{\mathrm{A}}$ is incident on a small aperture. After passing through the aperture, the beam is no longer parallel but diverges at $1{^\circ}$ to the incident direction. What is the diameter of the aperture?
A) 180m
B) 18$\mu m$
C) 1.8m
D) 0.18m
Explanation
(b) From diffraction at a single alit, size if aperture,
$a = \frac{\lambda}{\sin\theta}$
$a = \frac{3141.59 \times 10^{- 10}}{\sin{1{^\circ}}} = 18 \times 10^{- 6}m = 18\mu m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.