Main Page | See live article | Alphabetical index In telecommunication, a conservation of radiance is a basic principle of optics, that no passive optical system can increase the quantity L /n 2, where L is the radiance of a beam and n is the local refractive index. Note: "Conservation of radiance" was formerly called "conservation of brightness" or the "brightness theorem." Source: from Federal Standard 1037C and from MIL-STD-188 This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.