Reflection is of considerable importance for sound transmission and for the transmission of light in fiber optic cables. Reflection can also cause problems, for example, with excessive echoes in a room or glare from a computer screen. It accounts for the action of a prism splitting white light into its rainbow of colors. Refraction also causes the focusing or spreading of light when it passes through a convex or a concave lens. Color is the sensation registered when light of different wavelengths is perceived by the brain.
Color is observed in objects that reflect or emit certain wavelengths of light.
Reflected color results when an object does not absorb, but reflects the wavelength of light that strikes it. Emitted color results when a molecule is excited by some energy and then returns to its unexcited state, emitting the excess energy in the form a characteristic wavelength of visible light. Colors can be specified precisely in terms of the wavelengths and intensities of their component light. Such measurements are sometimes displayed in emission and remission curves. For this reason, color vision is said to be trichromatic.