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Asked in GSEB Board March 2023 · Single slit diffraction
Given: a slit of width a lit by a parallel beam of wavelength λ.
Idea: the beam spreads out to the first minimum, where light from the two edges of the slit differs in path by one whole wavelength: a sin θ=λ.
The angle is small in any practical case, so sin θ≈θ.
θ≈λ/a.
That single ratio is the whole of diffraction in one line: the wider the slit compared with the wavelength, the less the beam spreads, which is why we do not notice light bending round everyday objects.
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