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Home Minds On Light Waves and Colors Mission LC4 Complementary Colors of Light Help Help 7

Mission LC4 Complementary Colors of Light

The Question

Three colored spotlights - red, green and blue - with equal intensities are used to shine white light upon a blue shirt. The shirt appears blue because it absorbs the ____ light and reflects the ____ light.

Dig that Diagram

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.

Physics Rules

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.

Think About It

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 blue, then only the blue light of red, green and blue incident light was reflected. So if only the blue was reflected, then what happened to the red and green light? It was subtracted or absorbed. So red and green light - also known as yellow light - are absorbed by a shirt that looks blue. Now think about the color wheel shown in the Dig That Diagram section and you will see the big idea. Yellow light - the complement of blue light - is absorbed when a shirt appears blue in the presence of white light.

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