What must be the ratio of the slit width to the wavelength for a single slit to have the first diffraction minimum at 45°?

Q.13 What must be the ratio of the slit width to the wavelength for a single slit to have the first diffraction minimum at 45°?

Doubtly Asked 28 Oct 2026 Board exam · July 2025 hsc 12th Save WhatsApp Report

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Answer: \(\dfrac{a}{\lambda} = \sqrt2 \approx 1.414\)

For the first minimum in single slit diffraction, \(a\sin\theta = \lambda\).

\[\frac{a}{\lambda} = \frac{1}{\sin45^\circ} = \frac{1}{1/\sqrt2} = \sqrt2 = 1.414\]

Doubtly AI · 28 Oct 2026 AI-verified · Oct 2026 Report

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