Let it shine!

Ad­mire the most in­cred­i­ble iri­des­cent an­i­mals

World of Animals - - Contents - Words Vic­to­ria Williams

In most species, or­ganic com­pounds called pig­ments cre­ate their colours and pat­terns, but there are a few that do things dif­fer­ently: the iri­des­cent an­i­mals.

Iri­des­cence is a phe­nom­e­non caused by the re­flec­tion and re­frac­tion of light waves, pro­duc­ing shim­mer­ing colours that seem to change de­pend­ing on the an­gle the sur­face is viewed from.

Feath­ers, scales, fur and ex­oskele­tons with com­plex struc­tures can all gen­er­ate this ef­fect. When light hits them some waves are re­flected straight off the outer sur­face, while oth­ers travel deeper un­til they’re re­flected away by an in­ner layer. When these waves meet they can can­cel each other out if their crests and troughs are out of sync (called de­struc­tive in­ter­fer­ence) or am­plify each other to pro­duce an unusu­ally strong re­flec­tion if they match up (con­struc­tive in­ter­fer­ence).

Iri­des­cence varies in its use­ful­ness. Some an­i­mals rely on it in their quest to se­cure a mate, oth­ers have to avoid it get­ting them into trou­ble, and the rest don’t seem to no­tice it at all.

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