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Asked in GSEB Board July 2022 · Single slit diffraction
Idea: for a single slit of width a the minima lie at a sin θ = nλ, so every width in the pattern is proportional to the wavelength.
On a screen at distance D the fringe width is (λ D)/a, so the widest fringes go with the longest wavelength.
Of red, green, yellow and violet, red has the longest wavelength, about 700 nm against about 400 nm for violet.
So red light gives the widest diffraction fringes, about 1.75 times as wide as violet in the same apparatus.
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