A parallel beam of light of wavelength λ is incident normally on a narrow slit. A diffraction pattern is formed on a screen perpendicular to incident beam. At second minimum the phase difference between rays coming from two edges of slit is:
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Question

A parallel beam of light of wavelength λ is incident normally on a narrow slit. A diffraction pattern is formed on a screen perpendicular to incident beam. At second minimum the phase difference between rays coming from two edges of slit is:

Options

G1 Physics · Accepted Answer

Step 1: n-th dark fringe for single slit obeys a sin θ = nλ. Step 2: At second minimum n = 2, edge-to-edge path difference Δ = 2λ. Step 3: Δφ = 2πΔ/λ = 2π × 2 = 4π. Final answer: (C) 4π.