Section 2 | Page 2

The human eye contains two basic types of light receptors: rods and cones. The rods are sensitive only to the presence of light, not color. The cones are sensitive to color. During normal daytime vision, it is the cones, not the rods, that actively contribute to vision. At night, the more sensitive rods take over and give us ônight vision.ö There are three groups of cones, each sensitive to a portion of the visible color spectrumùred light, green light and blue light. The brain receives signals from the cones, processes them, then evokes the sensation of color. Various combinations of light waves evoke the sensation of other colors.