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How does visible light work? How is it that color goes from waves to visible color in our sight?
Question Date: 2017-05-27
Answer 1:

Excellent question.

All light is some kind of wave, including visible light. Visible light is in fact only a very small part of what is known as the electromagnetic spectrum. The word "light" is more of a conversational term.

The electromagnetic spectrum is called so because the phenomena of electric and magnetic fields are very closely tied to each other, and are collectively described with what is known as Maxwell's equations.

The length scales on the electromagnetic spectrum range from wavelengths as large as sports fields (radio waves) to as small as atoms (x-rays). And yes, those are the same waves as what you would listen to on the radio of your car or what you get at the doctor's office to look at your bones. You can see the vast range here

As you can see, the visible spectrum only takes up a small portion of the expanse covered by the electromagnetic spectrum.

The reason we call it visible light is because it is light that is visible to the human eye. Otherwise, it is simply electromagnetic radiation of a particular wavelength.

To understand how color works, we need to look a little closer into how the human eye is constructed, see basic anatomy of the eye here

In the retina, there are cells known as photoreceptors that are responsible for our vision. Two types of photoreceptors exist- rods and cones. Rods are for vision are low light and don't contribute to color perception. Cones on the other hand are active a high light levels and contribute to color perception. These photoreceptors are color sensitive to three types of colors- blue(ish), green(ish), and red(ish). I add an "ish" because there is a distribution of wavelengths to which these photoreceptors are sensitive . Our perception of color happens when light strikes these photoreceptors and interact with the pigments inside.

It turns out lots of animals have cones that are receptive to wavelengths of light outside what we consider "visible light." Read more about it here . My favorite is the mantis shrimp. The Oatmeal (a webcomic) does a far better job at portraying the awesomeness that is the mantis shrimp, so I will let it speak for itself .

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