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Three colored spotlights - red, green and blue - with equal intensities are used to shine white light upon a green shirt. The shirt appears green because it absorbs the ____ light and reflects the ____ light.
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 Many students of physics have seen a diagram similar to the one shown at the right. The diagram depicts three circles colored with the primary colors of light - red, green and blue. The primary colored circles overlap to produce other colors of light - known as the secondary colors of light: cyan, magenta and yellow. Complementary pairs of light colors are those colors that are exactly opposite each other on the diagram: red and cyan, magenta and green, and blue and yellow.
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Color Subtraction and Complementary Colors:
An object that is observed to be a specific color when illuminated with white light has absorbed the complementary color of the observed color. White light or R+ G + B was incident on the object. One or more of the components of white light were absorbed or subtracted and the remaining light colors were reflected to the observer's eye.
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The color of a shirt is not in the shirt itself, but rather in the light that the shirt reflects. If red, green and blue light shine on a shirt and the shirt appears green, then only the green light of red, green and blue incident light was reflected. So if only the green was reflected, then what happened to the red and blue light? It was subtracted or absorbed. So red and blue light - also known as magenta light - are absorbed by a shirt that looks green. Now think about the color wheel shown in the Dig That Diagram section and you will see the big idea. Magenta light - the complement of green light - is absorbed when a shirt appears green in the presence of white light.
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