What is the wavelength of magenta? (2019)
thoughtco.com
thoughtco.com
"Have you ever tried to find the color magenta on the visible spectrum? You can't do it! There is no wavelength of light that makes magenta. So how do we see it? Here's how it works...
You can't find magenta in the visible spectrum because magenta cannot be emitted as a wavelength of light. Yet magenta exists; you can see it on this color wheel.
Magenta is the complementary color to green or the color of the afterimage you would see after you stare at a green light. All of the colors of light have complementary colors that exist in the visible spectrum, except for green's complement, magenta. Most of the time your brain averages the wavelengths of light you see in order to come up with a color. For example, if you mix red light and green light, you'll see a yellow light. However, if you mix violet light and red light, you see magenta rather than the average wavelength, which would be green. Your brain has come up with a way to bring the ends of the visible spectrum together in a way that makes sense. Pretty cool, don't you think?"
Not really your brain, more your eyes.
Our eyes are not spectrographs: they don't measure the level of every frequency of light. Instead, (most) humans are trichromats, meaning we have three types of color receptors (the cone cells). Each type has a different sensitivity curve. For trichromat humans, one type is most sensitive around red (~650nm), one is most sensitive around green (~550nm), and one is most sensitive around blue (~450nm). These sensitivity curves overlap, so photons between 650nm and 550nm will stimulate both the red and green cones.
This means it's possible to simulate a single frequency between two adjacent types with two (or more) frequencies. For example, red light plus green light can also stimulate these cones in exactly the same way as true yellow (580nm), so there's no way for the human eye to distinguish between them. This is the basis of most display (and process color printing) technologies. An eye with more types of color receptors would not be fooled as easily.
Magenta is what we perceive when red and blue cones are both stimulated simultaneously in a way that is not possible from a single wavelength, as their sensitivity curves don't overlap. So when you see magenta, you're seeing at least two different wavelengths of light. With hues not between red and blue on the color wheel, it's possible that there's only one wavelength responsible (but it's also possible that it's a combination of wavelengths).
this is an oversimplification -- blue is actually completely overlapped by the other two cone types, but they have very low sensitivity in most of the blue range.
Only the fully saturated rainbow colors ROYGBIV are spectral colors. Indigo is deep blue. Violet, borderline between visible and UV light, is a single wavelength, but it excites the tail of our eye's Red cones, so appears bluish-purple.
The CIE Chromaticity Diagram https://en.wikipedia.org/wiki/Chromaticity shows it best, where the spectral colors form the curved outside, and the nonspectral colors are the straight 'line of purple' and all interior colors.
It is surprising that green's (~495-565 nm) complementary colors are all on the nonspectral line of purples (draw line from purple's corner endpoint, through the white point, to corresponding green).
Am I supposed to see a color wheel somewhere on the page? Or is this referring to that stock photo with a bunch of pencils?