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A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The radiation emitted by a black body in thermal equilibrium with its environment is called black-body radiation. The name "black body" is given because it absorbs all colors of light.
For a black body (a perfect absorber) there is no reflected radiation, and so the spectral radiance is entirely due to emission. In addition, a black body is a diffuse emitter (its emission is independent of direction). Blackbody radiation becomes a visible glow of light if the temperature of the object is high enough. [19]
The total power emitted per unit area at the surface of a black body (P) may be found by integrating the black body spectral flux found from Lambert's law over all frequencies, and over the solid angles corresponding to a hemisphere (h) above the surface.
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.
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.
The cause of death of a Black man found hanging in an abandoned Alabama house in September remains uncertain, after two conflicting autopsies. The state autopsy ruled that Dennoriss Richardson ...
The FBI is investigating the death of a Black man in Alabama, who was found hanging in an abandoned house, following a request from a local sheriff amid fears among community members who accuse ...
John Tyrrell, a 46-year-old North Cape May man and registered sex offender, reportedly found the woman’s body and was later arrested for allegedly interfering in cops’ investigation. L C.