blackbody


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blackbody,

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.

Blackbody

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

blackbody

[′blak¦bäd·ē]
(thermodynamics)
An ideal body which would absorb all incident radiation and reflect none. Also known as hohlraum; ideal radiator.

blackbody

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 ?
In brief, within his first proof, Kirchhoff utilized transmissive plates to accomplish the proof, even if blackbody cavities must always be opaque.
DoD also supported the development of the water bath blackbody and various fixed-point blackbodies to provide source-based radiometric scales.
The infrared spectra are automatically averaged and integrated with respect to the blackbody spectrum at selectable temperature range.
Once the temperature reading on the liquid crystal thermometer has stabilized, aim your IR unit at the center of the blackbody, at no more than 1 inch away.
Isothermal Technology Ltd, a supplier in the field of calibration and thermocouple referencing equipment, have announced the publication of databook 4 -- covering their range of blackbody and thermocouple reference products.
A blackbody is a perfect emitter, with emissivity of 1.
Contract Awarded for Low temperature blackbody source
On the other hand, a hot neutron star can emit thermal or blackbody radiation in the frequency range of X-rays.
m] is the pore diameter; [epsilon] is the particle surface emissivity and as is the blackbody radiation constant.
This excess is thermal emission, also known as blackbody radiation.
For all eight SPDs, RGB light emitting diodes (LEDs) were mixed to create white light matching the chromaticity of a blackbody radiator at 3500 K as close as possible--actual measures at the observers' eyes were 3500 K [+ or -] 20 K, with [D.
Elements new to this edition include: 3G and 4G cell phone systems, the engineering of modern wireless communication systems, new material on Plank's law of blackbody radiation, an expanded chapter on antennas, and more discussion of shadowing correlations and their effect on cell phone system design.