iridescence

Iridescence in soap bubbles

A female Golden Stag Beetle has a highly iridescent shell

The iridescence of the Blue Morpho butterfly wings

The iridescent inside surface of a red abalone shell

Ammolite is a gemstone consisting of iridescent ammonite fossils

The wings of Tachinid fly demonstrate iridescent colors that are due to the surface structures

Tapetum lucidum dissected from a calf's eye, appearing black and blue due to iridescence

Iridescence is generally known as the property of certain surfaces which appear to change colour as the angle of view changes. Iridescence may be seen commonly in soap bubbles, butterfly wings and sea shells.

Description

Iridescence (also known as goniochromism) is an optical phenomenon of surfaces in which hue changes in correspondence with the angle from which a surface is viewed.

Iridescence is caused by multiple reflections from multi-layered, semi-transparent surfaces in which phase shift and interference of the reflections modulates the incident light (by amplifying or attenuating some frequencies more than others). This process is the functional analog of selective wavelength attenuation as seen with the Fabry-Pérot interferometer.

Etymology

The word iridescence is derived in part from the Greek word iris (pl. irides), meaning "rainbow", which in turn derives from the goddess Iris of Greek mythology, who is the personification of the rainbow and acted as a messenger of the gods. Goniochromism is derived from the Greek words gonia, which means angle, and chroma, which means color.

Photography

Conventional photography only records the specific effect of iridescence, just as it only captures the effect of two dimensions; however, iridescence can be reproduced by holography (which includes phase information).

Examples

• the wings of certain insects, such as the Morpho butterfly.
• the black feathers of crows, starlings and grackles. Also the raven
• the shells of some mollusks such as abalone
• in animals, the tapetum lucidum, present in the eyes of many vertebrates
• pearlescent paints or interference pigments sometimes used for custom paintjobs on cars

See also

• Cloud iridescence
• Dichroic filter
• Dichroism
• Iridocyte
• Thin-film optics

External links

Wikimedia Commons has media related to: Iridescence

• Living photonic crystals
• A 2.2 MB GIF animation of a morpho butterfly showing iridescence
• "Article on butterfly iridescence"