Thin-film interference

Common card · No. 233373

Thin-film interference occurs when light waves reflected by the upper and lower boundaries of a thin film interfere with one another, increasing reflection at some wavelengths and decreasing it at others. When white light is incident on a thin film, this effect produces colorful reflections. Thin-film interference explains the multiple colors seen in light reflected from soap bubbles and oil films on water and also many colors found in nature. It is also the mechanism behind the action of antireflection coatings used on glasses and camera lenses. If the thickness of the film is much larger than the coherence length of the incident light, then the interference pattern will be washed out due to the linewidth of the light source. The reflection from a thin film is typically not individual wavelengths as produced by a diffraction grating or prism, but rather are a mixture of various wavelengths. Therefore, the colors observed are rarely those of the rainbow, but rather browns, golds, turquoises...

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