For a parallel beam of monochromatic light of wavelength λ, diffraction is produced by a single slit whose width a is of order wavelength. If D is screen distance from slit, width of central maximum is:
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Question

For a parallel beam of monochromatic light of wavelength λ, diffraction is produced by a single slit whose width a is of order wavelength. If D is screen distance from slit, width of central maximum is:

Options

G1 Physics · Accepted Answer

Step 1: The first minima on opposite sides obey a sin θ = ±λ. Step 2: For small θ, positions y₁ = ±Dλ/a. Step 3: Central maximum width is distance between these minima: 2Dλ/a. Final answer: (A) 2Dλ/a.