Today, I researched…IRIDESCENCE
HERE’S WHAT I FOUND:
Blue Morpho butterfly
(Morpho menelaus)
http://www.webexhibits.org/causesofcolor/15A.html
What is iridescence?
The wings of butterflies and moths consist of a colorless translucent membrane covered by a layer of scales (the name of the order is Lepidoptera, meaning "scaly wings"). Each scale is a flattened outgrowth of a single cell and is about 100 µm long and 50 µm wide. The scales overlap like roof tiles and completely cover the membrane, appearing as dust to the naked eye.
The iridescence is caused by multiple slit interference. Sunlight contains a full range of light wavelengths. "Interference" occurs when light hitting the wing interacts with light reflected off the wing.
Light is a wave. If the crests and the troughs of the waves are aligned, or in phase, they will cause constructive interference, and iridescence is the result. One light wave hits the first groove, and a second light wave travels half of a wavelength to another groove, and is then reflected back in phase with the first.
If the crest of one wave meets the trough of another wave (out of phase), they will cancel each other out, as destructive interference occurs.
http://www.webexhibits.org/causesofcolor/15A.html
Iridescence as a result of interference
We’re captivated when we see something in nature with a multitude of colors, or when the colors seem to change depending on our point of view. Whether we’re looking at pearl and mother-of-pearl, the transparent wings of houseflies and dragonflies, the near-metallic colors of scales on beetles and butterflies, or the feathers of hummingbirds and peacocks, we are immediately drawn to their iridescence (from the Latin word, "iris," meaning rainbow).
Although the iridescence of these natural wonders are a result of "structural colors," rather than pigment molecules, iridescence takes other forms as well. For example, light waves can interfere with one another, causing the iridescent colors you see in a layer of oil on a wet pavement or in the surface of a soap bubble.
Other examples of iridescence caused by interference include ice and crumpled cellophane, which will produce iridescent colors in polarized white light. Because they are optically anisotropic (they have different optical properties for light from different directions), they undergo double refraction. In contrast, the iridescent colors in opals, CDs, and DVDs that change with viewing angle is attributed to diffraction (the diffracted rays interfere to produce the colors).
http://www.webexhibits.org/causesofcolor/15.html
Japanese beetle (Popillia japonica)
http://www.webexhibits.org/causesofcolor/15D.html
Tiger beetle (Cicindelinae)
http://www.webexhibits.org/causesofcolor/15D.html
Bubbles
http://www.webexhibits.org/causesofcolor/15E.html
Mother-of-pearl is the name commonly given to shells coated in a deposit of nacre, which is iridescent.
http://www.webexhibits.org/causesofcolor/15B.html
Peacock spreading its feathers
http://www.webexhibits.org/causesofcolor/15C.html
Iridescence: How Nature Stages Her Most Colorful Light Show
By Ivan Amato
June 14, 1995
These are examples of one of nature's most spectacular optical tricks -- creating color without pigment. It's a natural light show in which waves of ordinary light are separated, combined, reflected and otherwise manipulated to create a phenomenon called iridescence. The word comes from Iris, the Greek goddess of the rainbow. Light comes in many wavelengths, each corresponding to a specific color. In the range of hues visible to the human eye, violet results from the shortest wavelengths and red from the longest. Ordinary light, sometimes called white light, is a mixture of different colors. Thus, when an object appears a certain color, it is because it absorbs most wavelengths and reflects only some to our eyes to produce the color we see. Iridescent objects do something very different. They unmix the brew of colors in white light by quelling some and intensifying others and then send the result to our eyes. The result is a brilliance, an intense, penetrating color that no simple reflection of light can achieve. Three centuries ago, the great English scientist Isaac Newton, thinking about the iridescent colors of peacock feathers, surmised that they were not produced by colored substances. He speculated that such colorful effects come from the way light interacts with tiny, invisible shapes of the objects. Physicists now know that is exactly what happens. The colors are produced by the way certain kinds of surfaces reflect light. There are two kinds of surfaces that can produce iridescence -- thin films such as those of a soap bubble and microscopic wrinkles or grooves such as those built into the scales of a butterfly….Newton had good intuition about peacock feathers. But before researchers could understand the phenomenon better, it took a new understanding of the wave-nature of light and the evolution of the scanning electron microscope (SEM) in this century.
https://www.washingtonpost.com/archive/1995/06/14/iridescence-how-nature-stages-her-most-colorful-light-show/f51cccf8-49ba-4074-88d6-49966a1cb4f7/