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Thin Film Interference. Soap Film – Why Color?. iridescence. Reflection and Phase. t. Thin Film Interference. Some light reflects off top layer, some off bottom layer. If crest meets trough destructive interference. If crest meets crest (trough meets
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Soap Film – Why Color? iridescence.
Thin Film Interference Some light reflects off top layer, some off bottom layer. If crest meets trough destructive interference If crest meets crest (trough meets trough) constructive interference
If remove (by destructive interference) a color from white light, will see the complementary color. ex., if yellow light is cancelled, will see blue
What determines the color seen? Thin Film Film material (n) and thickness (t) Angle viewed at
(assume light strikes perpendicular) extra distance (ABC) = 2t phase shift 2t t
phase shift 2t
λ is the wavelength in the film λair λn = --- n
A soap bubble (n = 1.35) appears green (λ = 540 nm) at the point on its front surface nearest the viewer. What is its minimum thickness? 1.0 x 107 m
Stealth Bomber Eliminate radar through thin-film interference
Coated lens reduces reflections through thin-film interference.