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From radiant peacock feathers and shiny beetle shells to bubbles and dirty puddles in the road, iridescence is a mind-blowing phenomenon that brings a little more color to nature. But all those colors aren’t actually there. You see nature is a bit of a physicist with iridescence being a physics trick it plays on us. Let me explain!
What is Iridescence?
Iridescence is a beautiful optical phenomenon where surfaces appear to change color based on the angle of a light source or a viewer’s perspective. As the observer’s perspective changes the colors also seem to change and the same is true if a light source is moved around,
How Does Iridescence Work?
Most colors we see are caused by pigments that absorb certain wavelengths of light. Whatever wavelength of light is least absorbed or most reflected becomes the color we observe. Iridescence, however, is a form of structural coloration. The colors aren’t caused by pigment but rather by the physical structure of the surface. Iridescent surfaces have microscopic structures that refract and reflect light. When light hits these surfaces, it bounces between multiple layers and interferes with itself. This interference causes certain wavelengths to amplify or cancel out, creating shifting colors as the angle changes.
Iridescence in Birds
Photo by Chris Charles on Unsplash
Let’s look at the smallest member of the living dinosaur family: the hummingbird. You’ll notice they have some amazing colors, largely used to attract mates as they may indicate the best genes or the best ability to survive. Three things make up the basis of iridescence in these birds: keratin, melanin, and air. The feathers have multiple microscopic layers that refract and reflect light causing a myriad of colors to show. This creates the shimmering and changing colors we see as we look at hummingbirds from different angles. Another example is the feather of a peacock. The feather’s microscopic layers of keratin (the same protein that makes up our hair and nails) reflect light at varying angles, causing the vibrant greens, blues, and purples we see.
Photo by ricardo frantz on Unsplash
Iridescence in Insects
Photo by Nora Jane Long on Unsplash
Photo by Stephen Hocking on Unsplash
Butterflies like the morpho have scales on their wings that contain tiny structures, which create a stunning metallic blue effect. Beetles look like they were painted by God Himself. The outer layer of a beetle's body is made of a super stiff polymer known as chitin that refracts light whenever it hits it. The different arrangements of the layers in chitin create the varying range of colors that beetles show. The shiny beetle bodies serve as camouflage, attract mates, and even help in thermoregulation.
Human-made Iridescence
Iridescent materials are found in fashion, cosmetics, and even architecture. Special films and coatings on sunglasses, makeup, and car paint mimic natural iridescence, offering vibrant, multidimensional color.
Conclusion
Iridescence plays a significant role in biology, communication, and defense in nature. Animals use it to attract mates, scare off predators, and even regulate temperature by reflecting specific wavelengths of light. Beyond biology, iridescence has inspired scientific and technological advances. Engineers, for example, are studying butterfly wings to create more efficient light-reflective surfaces for solar panels.
In essence, iridescence demonstrates the incredible power of light manipulation in nature and design. It’s a reminder of how much beauty and complexity can emerge from the simplest interactions of light and structure.
Reference List
Be Smart (2023). The Science of Iridescence is INCREDIBLE. [online] YouTube. Available at: https://www.youtube.com/watch?v=wK7XjHbt4Z0 [Accessed 17 May 2024].
Stuart-Fox, D., Ospina-Rozo, L., Ng, L. and Franklin, A.M. (2021). The Paradox of Iridescent Signals. Trends in Ecology & Evolution, 36(3), pp.187–195. doi:https://doi.org/10.1016/j.tree.2020.10.009.
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