Light with wavelength 500 nm falls on a slit of width 10 μm at an angle 30° to its normal. Find the angular position of the first minima located on both sides of the central Fraunhofer maxima:-
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Question

Light with wavelength 500 nm falls on a slit of width 10 μm at an angle 30° to its normal. Find the angular position of the first minima located on both sides of the central Fraunhofer maxima:-

G1 Physics · Accepted Answer

For oblique incidence on a slit, the first minima satisfy a(sinθ−sin i)=±λ. Here a=10 μm, λ=0.5 μm and i=30°, so λ/a=0.05. Thus sinθ=0.50±0.05, giving θ≈33.4° and 26.7°. Therefore the minima are approximately 33° and 27°. Option A.