Answers for the Teacher Only

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What Do You Think?

The answer to these questions lies in the field of both physiology and physics. The human eye and brain respond to the wavelength of light by producing the sensation of color, and each wavelength produces a distinct color, as seen in the spectrum of sunlight formed by a prism. (Recall that the index of refraction of the prism is a function of the wavelength of light.) The nature of the light-sensitive cells in the eye, together with the structure of the brain, determine in a complex way the color we see. Mixing paints produces color subtraction, because only light that can be transmitted by both paints is seen (the other colors are subtracted out). Overlapping lights in a theater produce color addition, since more light is reflected. The eye and brain do the rest to produce the colors we see.