Post on 29-Dec-2015
Thin Film Interference
Some light reflects off top layer, some off bottom layer.
If crest meets trough destructive interference
If crest meets crest (trough meetstrough) 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
Thin Film
What determines the color seen?
Film material (n) and thickness (t)Angle viewed at
(assume light strikes perpendicular)
t
extra distance (ABC) = 2t
Both rays
One ray
1λ, 2λ, 3λ, …
½λ, 3/2 λ,
5/2λ,…
phase shift
2t
Both rays
One ray
1λ, 2λ, 3λ, …
constr. inter.
destr. inter.
½λ, 3/2 λ,
5/2λ,…
destr. inter.
constr. inter.
phase shift
2t
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-filminterference