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This page was last edited on 15 June 2004, at 04:40 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may ...
Black hole greybody factors are functions of frequency and angular momentum that characterizes the deviation of the emission-spectrum of a black hole from a pure black-body spectrum. As a result of quantum effects, an isolated black hole emits radiation that, at the black-hole horizon, matches the radiation from a perfect black body. [1]
Greys are typically depicted as grey-skinned, diminutive humanoid beings that possess reduced forms of, or completely lack, external human body parts such as noses, ears, or sex organs. [3] Their bodies are usually depicted as being elongated, having a small chest, and lacking in muscular definition and visible skeletal structure. Their legs ...
A grey body is one where α, ρ and τ are constant for all wavelengths; this term also is used to mean a body for which α is temperature- and wavelength-independent. A white body is one for which all incident radiation is reflected uniformly in all directions: τ = 0, α = 0, and ρ = 1. For a black body, τ = 0, α = 1, and ρ = 0. Planck ...
A so-called grey body is a body for which the spectral emissivity is independent of wavelength, so that the total emissivity, , is a constant. [3]: 71 In the more general (and realistic) case, the spectral emissivity depends on wavelength.
Brightness temperature or radiance temperature is a measure of the intensity of electromagnetic energy coming from a source. [1] In particular, it is the temperature at which a black body would have to be in order to duplicate the observed intensity of a grey body object at a frequency . [2]
This type of theoretical model, with frequency-independent emissivity lower than that of a perfect black body, is often known as a grey body. For frequency-dependent emissivity, the solution for the integrated power depends on the functional form of the dependence, though in general there is no simple expression for it.
Emissivity of a body at a given temperature is the ratio of the total emissive power of a body to the total emissive power of a perfectly black body at that temperature. Following Planck's law , the total energy radiated increases with temperature while the peak of the emission spectrum shifts to shorter wavelengths.