alleryThe width of the central maximum in single-slit diffraction on a screen at distance D is
Aλ D / a
Bλ D × a
Ca D / λ
D2 λ D / a
Answer & Solution
Correct answer: D. 2 λ D / a
1. First minima are at ±λ/a (small-angle approximation).
2. On a screen at distance D, they lie at ±λD/a.
3. Width of central maximum = 2 × λD/a = 2λD/a.
4. Central maximum is thus twice as wide as the successive fringes.
_Source: syllabus Physics, Ch 10 "Wave Optics", §10.6_
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