If I₀ is the intensity of the principal maximum in a Fraunhofer single-slit diffraction pattern, what is the intensity of the first secondary maximum?
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Question

If I₀ is the intensity of the principal maximum in a Fraunhofer single-slit diffraction pattern, what is the intensity of the first secondary maximum?

G1 Physics · Accepted Answer

For a Fraunhofer single slit, I/I₀=(sinα/α)². The first secondary maximum lies near α=3π/2, so I₁/I₀≈[1/(3π/2)]²=4/(9π²). Option D.