Light Theory Explains Mixed Colors Puzzle: When White is Black
Why you can't mix colors to get white
Remember, back in grade school, when the teacher used a prism to explain light theory, and magically show all the colors that were hidden in a beam of white light? And remember when they explained that if you put all those colors together again they would turn back into a white light? Well then, why doesn't the same thing work for colors of real stuff, like; paint, or chalk, or crayons? Why do you just get a black or grey mess when you mix the same colors using paint?
Is the theory of light really a puzzle that only works for light rays? Are the colors of light the only ones that don't turn white into black? The answer to those questions is as simple as understanding it's an "apples to oranges" comparison; the colors of light and the colors of stuff - like paint, are not the same.
The Primary Colors We See - Red Green Blue
Your teacher might have used a dark box, a flashlight, and a prism to show the colors that were hiding inside white light, (like the photo on the right), and they probably explained that all those different colors came from just three primary colors; red, yellow, and blue. For grade-schoolers it was a magic moment, the prism was like a wizard's crystal, revealing secrets that couldn't be seen without it.
The teacher's explanation that it was refraction - the bending of light, was probably lost in that moment of wonder. And they probably didn't even mention that what you were seeing was the due to the additive color theory.
Three Primay and Three Secondary
The visible color spectrum includes 6 distinctive colors, as shown above, all made from the combination of the three primary colors; red, blue, yellow, and the three secondary colors; green, orange, purple, and an almost unlimited number of shades in-between.
But Wait! Aren't the three primary colors red, green, and blue?
Yes, and no. Yes because they are the three colors the cone receptors in our eyes are able to perceive. Our brains interpret every other color as some combination of those three. It may seem odd to discuss colors as if they could not be seen, but in reality, the primary color green is there because of those receptors, green is actually a mix of blue and yellow, not a primary color.
Back to the visible color spectrum...
The "red" end of the spectrum continues into infra-red range of colors, and the "purple" end into the range of ultra-violet colors. (remember those party black-lights and white socks)
So why isn't there an infra-red or ultra-violet color of paint? Because material colors, like paint, are pigment colors, not light colors, and they are ruled by the subtractive color theory.
Light (Additive) vs. Pigment (Subtractive) Color Theories
The colors of light and the colors of pigments might look the same, but that's because you are only seeing the visuals of the colors. When the properties of the colors, what they actually are, are examined, they are quite different, and the reason you can add all of one together to get white yet adding all the colors of the other returns black, is easily understood.
The Light Color Theory is Additive
The colors of light are made from different wave patterns of light, not from any form of pigmentation, like paints. That is why when you see a white light shown through a prism, you see the different colors that are in it. What you are seeing are the different wave lengths of light in that white beam, as they actually are when they are separated by the refraction of the prism.
The color theory of light is called additive because you are "adding" the wave length of one color to the wave length of another color, and the sum is a third color. Keep adding until you have added all the color's wavelengths - and the resulting sum is the wave length of white light. Magic! Or so it seems. Until you understand that white is not "0," the absence of color, but "10," (symbolic number), the sum of all colors.
The Pigment Color Theory is Subtractive
Pigment colors are based on their reflective properties, rather than their wave length. A black surface is the least reflective, and most absorptive, so a black surface will absorb most of the light that hits it - displaying the least color, black. Whereas a white surface is just the opposite, reflecting most of the light, thus displaying a white color.
A pigmented surface, green for instance, will absorb most of the non-green colors in light, and reflect the greens, thus the color green is seen. The brightness and intensity of the light will determine the shade of green you see.
Let Bill Nye, the Science Guy Explain It To You
Mixing Pigment Colors vs. Light Colors
So you can see that trying to compare the mixing results of colors depends on the origin of the colors. Mixing colors of light vs. mixing pigmented colors and trying to get the same results is a case of mixing apples and oranges, they just are not the same thing.
F.Y.I - To add a little more confusion...
Pigment colors are essentially coating colors, the two primary coatings being paint, and ink. And wouldn't you know it - they have different primary colors! As a computer user you are probably also a printer user, so the names of these primary colors might be familiar to you: Cyan, Magenta, and Yellow. Along with Black they form the CMYK, (K for black), color standard of the industry, and the primary ink colors in your printer.
Now you know why black is the absence of color, and why it isn't, and why white is the sum of all colors, unless it isn't. It all depends on whether you are talking apples or oranges.
About the Author
Reporting for the Daily Constitutional, and providing articles for various online publishing sites are my primary work responsibilities, but it is the freelance editorials from the Curmudgeon's desk that provide the most satisfaction. - GAA
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*Composite image component source citations: Creative Commons images from:commons.wikimedia.org, flickr.com/creativecommons, search.creativecommons.org, http://googlesystem.blogspot.com/2009/06/find-creative-commons-images-in-google.html, and personal art and graphic programs: GreenStreet Clipart, Print Shop, Art Explosion Pro Silver Edition Publishing program - *photo and image source credits: divider and separation images - http://gaanderson.hubpages.com
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