Light and Color - Mission LC7 Detailed Help

Three colored spotlights - red, green and blue - with equal intensities are used to illuminate a shirt with different colors of light. Yellow and magenta pigments are imparted to a shirt and it is then illuminated with red and green light. The shirt will appear ____.

(Note: The actual colors are randomly selected and may differ from those listed.)


Color Subtraction and Primary Pigments:
Primary pigments are painted onto or fixed within objects to subtract (absorb) one or more of the three primary colors of light. Any light color that shines on the paper and is not subtracted (absorbed) becomes reflected. This reflected light contributes to the color appearance of the object.

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 (C), magenta (M) and yellow (Y). These three colors - C, M, Y - are also the three primary colors of paint. The colors of light that they absorb are those directly opposite them on the color wheel. Cyan pigment absorbs red light. Magenta pigment absorbs green light. And yellow pigment absorbs blue light.

The two pigments in the paper are capable of absorbing two different primary colors of light. The color wheel in the Dig That Diagram section can help you determine which two colors of light the pigment can absorbed. If either one (or both) of those colors of light are shining on the paper, then it will not be reflected. Whichever light color(s) is/are reflected will determine the color appearance of the object. If both of the light colors are absorbed, then there is no light remaining to be reflected and the paper will appear black.


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