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Question: Answered & Verified by Expert
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?
PhysicsWave OpticsMHT CETMHT CET 2020 (13 Oct Shift 2)
Options:
  • A $\sin ^{-1}\left(\frac{1}{\sqrt{2}}\right)$
  • B $\sin ^{-1}(1)$
  • C $\sin ^{-1}\left(\frac{\sqrt{3}}{2}\right)$
  • D $\sin ^{-1}\left(\frac{1}{2}\right)$
Solution:
2428 Upvotes Verified Answer
The correct answer is: $\sin ^{-1}\left(\frac{1}{2}\right)$
$\sin \theta=\frac{\lambda}{a}=\frac{5 \times 10^{-7} \mathrm{~m}}{10^{-6} \mathrm{~m}}=0.5=\frac{1}{2}$
$\therefore \theta=\sin ^{-1}\left(\frac{1}{2}\right)$

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