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Related to blackbodies: Black body radiation


in physics, an ideal black substance that absorbs all and reflects none of the radiant energy falling on it. Lampblack, or powdered carbon, which reflects less than 2% of the radiation falling on it, crudely approximates an ideal blackbody; a material consisting of a carpetlike arrangement of vertically aligned carbon nanotubes was reported in 2008 to have a reflectance of 0.045%. Since a blackbody is a perfect absorber of radiant energy, by the laws of thermodynamics it must also be a perfect emitter of radiation. The distribution according to wavelength of the radiant energy of a blackbody radiator depends on the absolute temperature of the blackbody and not on its internal nature or structure. As the temperature increases, the wavelength at which the energy emitted per second is a maximum decreases. This phenomenon can be seen in the behavior of an ordinary incandescent object, which gives off its maximum radiation at shorter and shorter wavelengths as it becomes hotter and hotter. First it glows in long red wavelengths, then in yellow wavelengths, and finally in short blue wavelengths. In order to explain the spectral distribution of blackbody radiation, Max Planck developed the quantum theoryquantum theory,
modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity together form the theoretical basis of modern physics.
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 in 1901. In thermodynamics the principle of the blackbody is used to determine the nature and amount of the energy emitted by a heated object. Black-body radiation has served as an important source of confirmation for the big-bang theory, which holds that the universe was born in a fiery explosion c.13.7 billion years ago (according to current calculations). According to the theory, the explosion should have left a remnant black-body cosmic background radiation that is uniform in all directions and has an equivalent temperature of only a few degrees Kelvin. Such a uniform background, with a temperature of 2.7°K; (see Kelvin temperature scaleKelvin temperature scale,
a temperature scale having an absolute zero below which temperatures do not exist. Absolute zero, or 0°K;, is the temperature at which molecular energy is a minimum, and it corresponds to a temperature of −273.
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), was discovered in 1964 by Arno A. Penzias and Robert L. Wilson, who were awarded the Nobel Prize in Physics in 1978 for their work. Recent data gathered by the NASA satellite Cosmic Microwave Background Explorer (COBE) has revealed small temperature fluctuations in the radiation that are thought to be related to the "seeds" of stars and galaxies.


An ideal energy radiator, which at any specified temperature emits in each part of the electromagnetic spectrum the maximum energy obtainable per unit time from any radiator due to its temperature alone. A blackbody also absorbs all the energy which falls upon it. The radiation properties of real radiators are limited by two extreme cases—a radiator which reflects all incident radiation, and a radiator which absorbs all incident radiation. Neither case is completely realized in nature. Carbon and soot are examples of radiators which, for practical purposes, absorb all radiation. Both appear black to the eye at room temperature, hence the name blackbody. Often a blackbody is also referred to as a total absorber. See Heat radiation


An ideal body which would absorb all incident radiation and reflect none. Also known as hohlraum; ideal radiator.


1. A body whose radiation at each wavelength is the maximum possible for any electromagnetic radiator at that temperature.
2. A body that absorbs all light which is incident on it and consequently looks black.
References in periodicals archive ?
For infrared calibrations beyond 2 pm, DoD support enabled NIST to build the Low Background Infrared (LBIR) facility, consisting of two cryogenic chambers and two absolute cryogenic radiometers, for the calibrations of cryogenic blackbodies from facilities of DoD and its missile defense contractors [31,32].
The question was simple enough to answer, as blackbodies are always constructed from good absorbers.
At NIST these blackbodies are used to calibrate standard platinum resistance thermometers (SPRTs) to cover the temperature range from 15 [degrees]C to 170 [degrees]C and standard gold-platinum thermocouples to cover the range from 400 [degrees]C to 900 [degrees]C.
Laboratory blackbodies are specialized objects always made from relatively good emitters of radiation over the frequency range of interest, as well illustrated by the facts (see references within [8-12]).
The calibration methods used by the participating organizations included blackbodies or radiating panels to irradiate the sensors, and the heat-flux at the sensor was calculated by radiometric principles or reference standard calorimeters.
Max Planck recognized that blackbodies were complex devices, as the data provided for his analysis had been obtained by some of the premier experimentalists in Germany [11-13].
Since laboratory blackbodies must be Lambertian emitters [11, p.
That is why he advocated that optically thick gases could emit as blackbodies.
Conversely, it is known that laboratory blackbodies constructed from graphite, or soot (carbon black, lampblack), can reach rather high emissivities over certain frequencies [18-21].
The LLT facility, with variable-temperature water- and oil-bath blackbodies and cesium and sodium heat-pipe blackbodies, has been developed for calibration of pyrometers and sources in the temperature range from 288 K to 1223 K (140-142).
One could compute the spectral radiance of these blackbodies, but only as well as you knew what their temperatures actual were.
Experimental blackbodies of the 19th century were manufactured using either graphite, or soot [7], precisely because such carbon surfaces were not transparent and exceeded all others in being devoid of reflection.