Black body
Black body
A Black body (pronounced: /blæk bɒdi/) is a theoretical or model body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The term "black body" was introduced by Gustav Kirchhoff in 1860.
Etymology
The term "black body" was introduced by Gustav Kirchhoff in 1860. It comes from the concept that a perfect absorber appears completely black, as it reflects no light.
Definition
A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. A white body is one with a "rough surface that reflects all incident rays completely and uniformly in all directions."
Properties
A black body in thermal equilibrium (that is, at a constant temperature) emits electromagnetic radiation called Black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a specific spectrum and intensity that depends only on the temperature of the body.
Related Terms
- Black-body radiation: The type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, or emitted by a black body held at constant, uniform temperature.
- Planck's law: A law that describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T.
- Thermal equilibrium: A state in which all parts of a system are at the same temperature.
- Electromagnetic radiation: A type of wave that includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
External links
- Medical encyclopedia article on Black body
- Wikipedia's article - Black body
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