Black-body radiation

Black-body radiation is the <a href="/facts/Thermal_radiation/1PD9jtCv">thermal</a> <a href="/facts/Electromagnetic_radiation/Ynx7ujCW">electromagnetic radiation</a> within, or surrounding, a body in <a href="/facts/Thermodynamic_equilibrium/1D7nGm0d">thermodynamic equilibrium</a> with its environment, emitted by a <a href="/facts/Black_body/f0fHghDy">black body</a> (an idealized opaque, non-reflective body). It has a specific <a href="/facts/Continuous_spectrum/CYz0fv0d">continuous spectrum</a> that depends only on the body's <a href="/facts/Temperature/QyGe4gmj">temperature</a>.
A perfectly-insulated enclosure which is in thermal equilibrium internally contains blackbody radiation and will emit it through a hole made in its wall, provided the hole is small enough to have a negligible effect upon the equilibrium. The thermal radiation spontaneously emitted by many ordinary objects can be approximated as blackbody radiation.
Of particular importance, although planets and stars (including the <a href="/facts/Earth/HLLmDfj0">Earth</a> and <a href="/facts/Sun/CadPCVHh">Sun</a>) are neither in thermal equilibrium with their surroundings nor perfect black bodies, blackbody radiation is still a good first approximation for the energy they emit.
The term black body was introduced by <a href="/facts/Gustav_Kirchhoff/Ygfzlywy">Gustav Kirchhoff</a> in 1860. Blackbody radiation is also called <a href="/facts/Thermal_radiation/1PD9jtCv">thermal radiation</a>, cavity radiation, complete radiation or temperature radiation.

Black-body radiation open-in-new

Black-body radiation