Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Thin-film interference
open-in-new
<p>Thin-film interference is a natural phenomenon in which <a href="/facts/Light_wave/jeofpMn4">light waves</a> reflected by the upper and lower boundaries of a <a href="/facts/Thin_film/nSeoUT4Q">thin film</a> <a href="/facts/Interference_(wave_propagation)/lI5f78I4">interfere</a> with one another, increasing reflection at some <a href="/facts/Wavelength/kcJU0ymz">wavelengths</a> and decreasing it at others. When white light is incident on a thin film, this effect produces colorful reflections. </p><p>Thin-film interference explains the multiple colors seen in light reflected from <a href="/facts/Soap_bubble/eq1CIYkW">soap bubbles</a> and oil films on <a href="/facts/Water/0lkXnJPK">water</a>. It is also the mechanism behind the action of <a href="/facts/Antireflection_coating/BN2xVy4k">antireflection coatings</a> used on <a href="/facts/Glasses/ER3sFKmJ">glasses</a> and <a href="/facts/Camera_lens/TkL6sd1b">camera lenses</a>. If the thickness of the film is much larger than the <a href="/facts/Coherence_length/A845Dc1z">coherence length</a> of the incident light, then the interference pattern will be washed out due to the <a href="/facts/Linewidth/HuI4Bj5f">linewidth</a> of the light source. </p><p>The reflection from a thin film is typically not individual wavelengths as produced by a <a href="/facts/Diffraction_grating/TUcyt7Do">diffraction grating</a> or <a href="/facts/Prism_(optics)/eodBFF70">prism</a>, but rather are a mixture of various wavelengths. Therefore, the colors observed are rarely those of the rainbow, but rather browns, golds, turquoises, teals, bright blues, purples, and magentas. Studying the light reflected or transmitted by a thin film can reveal information about the thickness of the film or the effective <a href="/facts/Refractive_index/yjkzvgeE">refractive index</a> of the film medium. Thin films have many commercial applications including <a href="/facts/Anti-reflection_coating/BN2xVy4k">anti-reflection coatings</a>, <a href="/facts/Mirror/wMu4u6BB">mirrors</a>, and <a href="/facts/Optical_filter/WdCmGqaq">optical filters</a>. </p>