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black-body radiation

n. the electromagnetic radiation that would be radiated from an ideal black body; the distribution of energy in the radiated spectrum of a black body depends only on temperature and is determined by Planck's radiation law [syn: blackbody radiation]

Black-body radiation

Black-body radiation is the type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, or emitted by a black body (an opaque and non-reflective body), assumed for the sake of calculations and theory to be held at constant, uniform temperature. The radiation has a specific spectrum and intensity that depends only on the temperature of the body.

The thermal radiation spontaneously emitted by many ordinary objects can be approximated as blackbody radiation. A perfectly insulated enclosure that is in thermal equilibrium internally contains black-body radiation and will emit it through a hole made in its wall, provided the hole is small enough to have negligible effect upon the equilibrium.

A black-body at room temperature appears black, as most of the energy it radiates is infra-red and cannot be perceived by the human eye. Because the human eye cannot perceive color at very low light intensities, a black body, viewed in the dark at the lowest just faintly visible temperature, subjectively appears grey (but only because the human eye is sensitive only to black and white at very low intensities - in reality, the frequency of the light in the visible range would still be red, although the intensity would be too low to discern as red), even though its objective physical spectrum peaks in the infrared range. When it becomes a little hotter, it appears dull red. As its temperature increases further it eventually becomes blue-white.

Although planets and stars are neither in thermal equilibrium with their surroundings nor perfect black bodies, black-body radiation is used as a first approximation for the energy they emit. Black holes are near-perfect black bodies, in the sense that they absorb all the radiation that falls on them. It has been proposed that they emit black-body radiation (called Hawking radiation), with a temperature that depends on the mass of the black hole.

The term black body was introduced by Gustav Kirchhoff in 1860. Black-body radiation is also called complete radiation or temperature radiation or thermal radiation.

Usage examples of "black-body radiation".

Tom would have given a no-holds-barred lecture full of such terms as quantum efficiency, black-body radiation, and spectral sensitivity that would have convinced his audience that the subject was extremely complex (which was true enough) and wholly impossible for the layman to understand (which was quite false).

The energy density of black-body radiation goes up as the cube of the temperature&mdash.

The energy density of black-body radiation goes up as the cube of the temperature-that's the old StefanBolzmann law-but the number of photons goes up linearly with the temperature, too, so effectively it's a fourth-power increase inside the kugelblitz.

The energy density of black-body radiation goes up as the cube of the temperature-that’.

If you remember your black-body radiation, black is actually best in heat.

I turned in my panic to empty-field sources and black-body radiation.

The spectrum of black-body radiation at temperatures that close to absolute zero—.