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Explain why an extensive thin film appears black in reflected light?
written 4.5 years ago by
Pooja Joshi • 2.5k
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• modified 4.5 years ago |
Mumbai university > FE > SEM 2 > Applied Physics II
Marks: 3M
Year: Dec 2013
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written 4.5 years ago by
Pooja Joshi • 2.5k
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The path difference on reflected side of thin film between reflected rays BC and EF is given by:-
$Δ = 2μ + cos r ± \frac{λ}{2}$ {μ = R.I of materials, r = Angle of refraction}
For an extensive thin film; t → 0
$Δ = ± \frac{λ}{2}$ which is the condition for destructive interference
Hence, extensive thin film appears black in reflected light.
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