Last week, our visitors discovered the phenomenon of iridescence on the scales of blue morpho butterfly wings. It turns out iridescence occurs a lot in nature! We can find beautiful examples of iridescence in mother of pearl shells, the feathers of peacocks and ducks, and even on some flies and beetles.
Some iridescent animals use their ability to reflect light to attract a mate. Male Anna’s hummingbirds will manipulate their feathers to produce quick flashes of bright red that they can direct towards a potential mate. Since the red color can only be viewed from a certain angle, the hummingbird nicely avoids also attracting a nearby predator.
Check out the wild and spooky iridescent mating dance of the “Superb Bird of Paradise” from Papa New Guinea.
After exploring some pictures and videos of iridescence, your students may be ready to experience it first hand. Your kids have probably been playing with iridescence all their short lives – all you need are bubbles!
Bubbles reflect light off two surfaces of soap sandwiching a layer of water. If the two reflected light wavelengths line up, you perceive a super intense color, this is called constructive interference. If the light waves reflected off the two surfaces don’t line up perfectly, they will cancel each other out, a phenomenon called destructive interference. In destructive interference the light waves become too mixed up and scrambled for your eyes to even perceive; the colors cancel each other out. The varying thickness of the bubble surface changes which light wavelengths get amplified and which get cancelled out. How many different colors can your students spot on the surface of a bubble? Do the colors change based on the angle of observation?
After exploring iridescence through bubbles, go on a nature walk to see if you can spot any iridescent wildlife.
Starlings, with their iridescent green and purple plumage, are all too easy to spot in New York. They were introduced to Central Park in 1890 by a Shakespeare fanatic who wanted to introduce every bird mentioned in Shakespeare’s plays to New York City. They went from 40 birds to 50 million birds a century later! Read more about their invasive introduction to Manhattan here.