Osm Physics by Ashish

Thin films show colours due to a fascinating optical phenomenon called thin-film interference . This is the same effect that produces the rainbow patterns on soap bubbles, oil slicks on puddles, and the shimmering iridescence on butterfly wings or peacock feathers. The Physics Behind It Wavelength-Dependent (Colour-Dependent) Effects Here's the key: the amount of interference depends on the wavelength of light (i.e., its colour). For a film of a given thickness: Some colours (wavelengths) experience constructive interference → they appear vivid Other colours experience destructive interference → they appear washed out or invisible The condition for constructive interference is roughly: 2 n t = m λ 2 n t = mλ where: t t = thickness of the film n n = refractive index of the film material λ λ = wavelength of light m m = an integer (order of interference) So a film of a particular thickness "selects" certain colours to brighten and others to suppress — giving it a specif...