There Are (No) Stupid Questions ... in Science by Leah Elson

Author:Leah Elson
Language: eng
Format: epub
Publisher: Blackstone Publishing
Published: 2023-05-24T00:07:23+00:00

How are all the colors of the rainbow contained in white light?

I totally understand the undertones of outrage when this question is asked. If you’ve had a cursory encounter with mixing paint colors, then you know that the combination of even a few of them can result in a drab muddy-brown hue. So it’s only natural—based on our firsthand finger-painting adventures—to be confused when we’re told that white light contains all the colors in our perceived visible spectrum. Shouldn’t the light, instead, be icky brown?

I find it best to begin with the basics, so let’s talk about the nature of white light. The light we perceive is also aptly called “visible light” and is part of the electromagnetic spectrum. It corresponds to wavelengths of radiation that fall in the middle of this spectrum, somewhere between super powerful gamma rays and long lumbering radio waves. Therefore, visible light is simply radiation that we have developed sensory receptors to be able to see. Some animals have gone a step further and can also visualize radiation in the ultraviolet or infrared parts of the electromagnetic spectrum as well.

Our range of visible light includes a multitude of frequencies. Human brains have been wired to interpret each of these frequencies as a distinct hue. So color can be perceived when any of these frequencies enter the eye.

Let’s consider a strawberry. The reason we see its bright color is because molecules in the skin of the strawberry have reflected a frequency of visible radiation that corresponds to the color red. The radiation bounces off the strawberry, enters our eye, and triggers a cascade of signaling to the brain, and the brain says, “Yep, that’s red.” We don’t see the strawberry as blue or purple or green because those frequencies were absorbed by the strawberry’s skin and, as such, never entered our eye for interpretation by the brain.

White light is what light looks like when none of the frequencies are being reflected or absorbed, and they’re all still packaged together. Remember: when photoreceptors of the eye are not being activated, the brain cannot interpret a distinct color. So the light is called “white.” But more accurately, it’s not really white as much as it is a non-photoreceptor-activating, colorless beam of electromagnetic radiation. If certain wavelengths aren’t bouncing off objects, then you won’t perceive an associated color.

Now, let’s circle back to the frustrations of mixing paints. The reason multiple colors of paint will yield icky brown is that multiple combined pigments will reflect different frequencies of light into your eyes, simultaneously, for a combined interpretation. And this combined interpretation, with the unchecked paint-mixing bravado of a novice, is usually quite hideous.

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