MHT CET · Physics · Wave Optics

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?

A \(\sin ^{-1}\left(\frac{1}{\sqrt{2}}\right)\)
B \(\sin ^{-1}(1)\)
C \(\sin ^{-1}\left(\frac{\sqrt{3}}{2}\right)\)
D \(\sin ^{-1}\left(\frac{1}{2}\right)\)

Verified Solution

Answer & Solution

Correct Answer

(D) \(\sin ^{-1}\left(\frac{1}{2}\right)\)

Step-by-step Solution

Detailed explanation

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

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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A parallel beam of monochromatic light of wavelength \(5 \times 10^{-7} \mathrm{~m}\) is incidentnormally on a single narrow slit of width \(10^{-3} \mathrm{~mm}\). At what angle of diffraction,the first minima is observed?

Step-by-step Solution

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?