A radiant source's emission of a distribution of energy (colors) arranged in order of wavelengths. This band of colors (a range of various kinds of light which might originate from any particular source, such as is produced when sunlight is refracted and dispersed by a prism) is comprised of red, orange, yellow, green, blue, indigo, and violet. A rainbow is such a natural display of the visible spectrum. Of all the colors in the visible spectrum, red has the longest wavelength at about 700 nanometers. Violet has the shortest at 400 nanometers. Just longer than red is infrared. Just shorter than violet are ultraviolet and then x-rays. The plural form can be either spectra or spectrums.Also see angstrom, color wheel, cool and warm colors, diffraction grating, palette, saturation, and ultraviolet.