Knowra Thin-film interference Thin-film interference Thin-film interference is the reinforcement or cancellation of light waves reflected from the upper and lower boundaries of a thin layer, producing wavelength-dependent brightness and color.
Optical path length : The distance light travels multiplied by the refractive index of the medium. It sets the phase difference accumulated by light traveling within the film.
Anti-reflective coating : An optical coating designed to reduce reflections through interference between waves reflected at its boundaries. A coating thickness can make reflected visible light cancel over a chosen wavelength range.
Soap bubble : A thin liquid film enclosing air, whose reflected light often displays shifting colors. Its changing thickness makes different wavelengths reinforce across the surface.
Diffraction : The spreading and interference of waves as they pass openings or encounter obstacles. Both effects create wavelength-dependent patterns, but diffraction arises from wavefront geometry rather than two film boundaries.
Phase shift : A change in the phase of a wave, often caused by reflection or propagation through a medium. Reflection at a boundary can reverse a wave, changing whether the two reflected waves reinforce.
Interference filter : An optical filter that transmits selected wavelengths using interference in thin layers or cavities. Layer thicknesses select which wavelengths pass through and which are reflected.
Oil slick : A thin layer of oil spread over water, often showing iridescent colors in reflected light. The oil-water and air-oil reflections interfere, producing bands of color.
Thin-film absorption : Wavelength-dependent attenuation of light as it propagates through a thin material layer. Absorption can color a film by removing wavelengths, unlike interference, which redistributes reflected intensity.
Constructive interference : Wave superposition that produces a larger amplitude when waves arrive in phase. Selected wavelengths become bright when the reflected waves arrive in phase.
Structural coloration : Color produced by microscopic structure affecting light rather than by selective absorption from pigments alone. Thin layers create vivid colors in soap bubbles, oil films, and some biological surfaces.
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