Iridescence

Iridescence is an optical effect in which a surface’s apparent color changes with viewing angle or illumination, usually because light interferes or diffracts.

Thin-film interference: Interference between light reflected from the upper and lower boundaries of a thin layer, producing wavelength-dependent colors. Many iridescent coatings arise when reflected waves from neighboring interfaces reinforce different colors at different angles.
Visible spectrum: The range of electromagnetic wavelengths detectable by human vision, roughly 380 to 700 nanometers. Iridescent hues arise from selectively directing portions of this wavelength range.
Morpho butterfly: A group of butterflies known for brilliant blue wings produced by microscopic scale structures. Its wing scales generate vivid directional color through multilayer and ridge structures.
Pigment: A material that produces color by selectively absorbing some wavelengths and reflecting or transmitting others. Pigment color usually remains more stable across viewing angles than structural iridescence.
Structural color printing: Color production by printing microscopic patterns that selectively scatter, diffract, or interfere with light. Printed structures can create durable colors without conventional dyes and pigments.
Diffraction grating: A structure with repeated grooves or lines that separates light into directions according to wavelength. Regular surface patterns can send different wavelengths toward the eye at different angles.
Wavelength: The spatial period of a wave, measured between successive corresponding points. Interference and diffraction select light according to wavelength, which perception maps to hue.
Peacock: A large pheasant whose male tail feathers bear eye-like markings with structural colors. Ordered melanin rods in feather barbules create angle-dependent greens and blues.
Diffuse reflection: Reflection in which light scatters in many directions from a rough surface. Diffuse scattering tends to suppress the sharply directional color shifts characteristic of iridescence.
Color-shifting ink: Ink containing optically active flakes that display different colors as viewing angle changes. Banknotes and secure documents use its angle-dependent appearance as a visible authentication feature.

Linked from 19 pages