GITAM, Department of Engineering Physics
Reflection in Thin Films
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Rays 1 and 2
interfere -------------------------------- Wavelength inside film is smaller: l' = l / n n = index of refraction of film ------------------------------- Ray 1 suffers a phase change of 180 degrees |
Interference Condition for Thin Films
Phase Change on Reflection
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Reflected light will experience a 180 degree phase change when it reflects from a medium of higher index of refraction and no phase change when it reflects from a medium of smaller index. This phase change is important in the interference which occurs in thin films, the design of anti-reflection coatings, interference filters, and thin film mirrors.
Interference Projects
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 Thin film of air between slides produces interference pattern. |
Light Interference in Soap Film
 Soap film on rectangular frame is similar to glass plates with air film between them. |
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Thin Film Interference in Peacocks
 Iridescence of peacock feathers is caused by light reflected from complex layered surface |
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