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Unformatted text preview: y far from sources Need to know phase difference
Very far: angle ACB is very small normal Path AC and BC are equal
Path difference: ∆l = d sin(θ ) If ∆l = 0, λ, 2λ, 3λ, 4λ … - maximum
If ∆l = λ/2, 3λ/2, 5λ/2 … - minimum Diffraction: Interference due to an Aperture mλ = d sin(θ )
Or Fourier transform of Aperture function Spatial Coherence
Each point on extended
source is independent source
If extended source is small
and the slits are far away
interference can still occur
≫ Beats (interference in time...
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