The diffraction pattern of a light of wavelength 400 nm diffracting from a slit of width 0.2 mm is focused on the focal plane of a convex lens of focal length 100 cm. The width of the 1st secondary maxima will be :
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Question

The diffraction pattern of a light of wavelength 400 nm diffracting from a slit of width 0.2 mm is focused on the focal plane of a convex lens of focal length 100 cm. The width of the 1st secondary maxima will be :

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G1 Physics · Accepted Answer

Width of 1st secondary maxima = λD/a Here, a = 0.2 × 10⁻³ m λ = 400 × 10⁻⁹ m D = 100 × 10⁻² m Therefore, width = (400 × 10⁻⁹ × 100 × 10⁻²)/(0.2 × 10⁻³) = 2 × 10⁻³ m = 2 mm