Wave optics

The path difference of two coherent waves
Δ_d = d2-d1
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The path difference of two coherent waves: interference maximum
Δ_d = k * λ
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The path difference of two coherent waves: interference minimum
Δ_d = (2k+1) * λ/2
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Thin-film interference: constructive (maximum)
2h n cos(β) = (2k+1) * λ/2
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Thin-film interference: destructive (minimum)
2h n cos(β) = k  λ
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Radii of Newton's rings
r = saknis(k*R*λ)
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Radii of Newton's rings
r = saknis((2k+1)*R*λ / 2)
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Light diffraction
l = d^2 / (4*λ)
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Diffraction grating: maximums (bright stripes)
d sin(φ) = k*λ
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Diffraction grating: minimums (dark stripes)
d sin(φ) = (2k+1)*λ/2
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