The several colored and other rays of which light is composed, separated by the refraction of a prism or other means, and observed or studied either as spread out on a screen, by direct vision, by photography, or otherwise. See Illust. of Light, and Spectroscope.
A luminous appearance, or an image seen after the eye has been exposed to an intense light or a strongly illuminated object. When the object is colored, the image appears of the complementary color, as a green image seen after viewing a red wafer lying on white paper. Called also ocular spectrum.
A wavelength or frequency band of electromagnetic radiation that contains information about the radiating source of energy. Optical astronomers rely on the spectrum of light from red to blue (visible spectrum) for detailed information carried by absorption or emission lines, color appearance and brightness. An optical instrument called a spectrograph refracts the light into a spectrum of color with a grating or prism.