Definitions for black body
This page provides all possible meanings and translations of the word black body
black body, blackbody, full radiator(noun)
a hypothetical object capable of absorbing all the electromagnetic radiation falling on it
"a black body maintained at a constant temperature is a full radiator at that temperature because the radiation reaching and leaving it must be in equilibrium"
A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. A black body in thermal equilibrium emits electromagnetic radiation called black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a spectrum that is determined by the temperature alone, not by the body's shape or composition. A black body in thermal equilibrium has two notable properties: ⁕It is an ideal emitter: it emits as much or more energy at every frequency than any other body at the same temperature. ⁕It is a diffuse emitter: the energy is radiated isotropically, independent of direction. An approximate realization of a black surface is a hole in the wall of a large enclosure. Any light entering the hole is reflected indefinitely or absorbed inside and is unlikely to re-emerge, making the hole a nearly perfect absorber. The radiation confined in such an enclosure may or may not be in thermal equilibrium, depending upon the nature of the walls and the other contents of the enclosure. Real materials emit energy at a fraction—called the emissivity—of black-body energy levels. By definition, a black body in thermal equilibrium has an emissivity of ε = 1.0. A source with lower emissivity independent of frequency often is referred to as a gray body. Construction of black bodies with emissivity as close to one as possible remains a topic of current interest. A white body is one with a "rough surface [that] reflects all incident rays completely and uniformly in all directions."
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