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  2. Black-body radiation - Wikipedia

    en.wikipedia.org/wiki/Black-body_radiation

    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]

  3. Kirchhoff's law of thermal radiation - Wikipedia

    en.wikipedia.org/wiki/Kirchhoff's_law_of_thermal...

    A body at temperature T radiates electromagnetic energy. A perfect black body in thermodynamic equilibrium absorbs all light that strikes it, and radiates energy according to a unique law of radiative emissive power for temperature T (Stefan–Boltzmann law), universal for all perfect black bodies. Kirchhoff's law states that:

  4. Emissivity - Wikipedia

    en.wikipedia.org/wiki/Emissivity

    Black soot absorbs thermal radiation very well; it has an emissivity as large as 0.97, and hence soot is a fair approximation to an ideal black body. [ 21 ] [ 22 ] With the exception of bare, polished metals, the appearance of a surface to the eye is not a good guide to emissivities near room temperature.

  5. Stefan–Boltzmann law - Wikipedia

    en.wikipedia.org/wiki/Stefan–Boltzmann_law

    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.

  6. Low emissivity - Wikipedia

    en.wikipedia.org/wiki/Low_emissivity

    Emissivity is the value given to materials based on the ratio of heat emitted compared to a perfect black body, on a scale from zero to one. A black body would have an emissivity of 1 and a perfect reflector would have a value of 0. Kirchhoff's law of thermal radiation states that absorption equals emissivity opaque (ε opaque) for every ...

  7. Black body - Wikipedia

    en.wikipedia.org/wiki/Black_body

    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.

  8. Thermal radiation - Wikipedia

    en.wikipedia.org/wiki/Thermal_radiation

    If the radiating body and its surface are in thermodynamic equilibrium and the surface has perfect absorptivity at all wavelengths, it is characterized as a black body. A black body is also a perfect emitter. The radiation of such perfect emitters is called black-body radiation. The ratio of any body's emission relative to that of a black body ...

  9. Effective temperature - Wikipedia

    en.wikipedia.org/wiki/Effective_temperature

    The effective temperature of the Sun (5778 kelvins) is the temperature a black body of the same size must have to yield the same total emissive power.. The effective temperature of a star is the temperature of a black body with the same luminosity per surface area (F Bol) as the star and is defined according to the Stefan–Boltzmann law F Bol = σT eff 4.