A parallel beam of monochromatic light of wavelength $5 \times 10^{-7} \mathrm{~m}$ is incident normally on…

A parallel beam of monochromatic light of wavelength $5 \times 10^{-7} \mathrm{~m}$ is incident normally on a single narrow slit of width $10^{-3} \mathrm{~mm}$. At what angle of diffraction, the first minima is observed?
  1. $\sin ^{-1}\left(\frac{1}{\sqrt{2}}\right)$
  2. $\sin ^{-1}(1)$
  3. $\sin ^{-1}\left(\frac{\sqrt{3}}{2}\right)$
  4. $\sin ^{-1}\left(\frac{1}{2}\right)$

Solution

$\sin \theta=\frac{\lambda}{a}=\frac{5 \times 10^{-7} \mathrm{~m}}{10^{-6} \mathrm{~m}}=0.5=\frac{1}{2}$ $\therefore \theta=\sin ^{-1}\left(\frac{1}{2}\right)$ *

Asked in: MHT CET 2020 (13 Oct Shift 2)

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