Consider diffraction by a slit of small width. O is point of central maxima; A is point closest to O where intensity is zero. Now if width of slit is increased slightly.
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Question

Consider diffraction by a slit of small width. O is point of central maxima; A is point closest to O where intensity is zero. Now if width of slit is increased slightly.

G1 Physics · Accepted Answer

For a single slit, first minimum satisfies y₁≈λD/a. Increasing slit width a makes y₁ smaller, so A moves toward O. The central amplitude is proportional to slit width, so its intensity increases. Hence option B.