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In its most general form, emissivity can be specified for a particular wavelength, direction, and polarization. However, the most commonly used form of emissivity is the hemispherical total emissivity, which considers emissions as totaled over all wavelengths, directions, and polarizations, given a particular temperature. [13]: 60
For example, white paint is quoted as having an absorptivity of 0.16, while having an emissivity of 0.93. [13] This is because the absorptivity is averaged with weighting for the solar spectrum, while the emissivity is weighted for the emission of the paint itself at normal ambient temperatures.
Thermal emittance or thermal emissivity is the ratio of the radiant emittance of heat of a specific object or surface to that of a standard black body.Emissivity and emittivity are both dimensionless quantities given in the range of 0 to 1, representing the comparative/relative emittance with respect to a blackbody operating in similar conditions, but emissivity refers to a material property ...
Emissivity can in general depend on wavelength, direction, and polarization. However, the emissivity which appears in the non-directional form of the Stefan–Boltzmann law is the hemispherical total emissivity, which reflects emissions as totaled over all wavelengths, directions, and polarizations. [3]: 60
The "mass emission coefficient" j ν is equal to the radiance per unit volume of a small volume element divided by its mass (since, as for the mass absorption coefficient, the emission is proportional to the emitting mass) and has units of power⋅solid angle −1 ⋅frequency −1 ⋅density −1. Like the mass absorption coefficient, it too ...
Low emissivity (low e or low thermal emissivity) refers to a surface condition that emits low levels of radiant thermal (heat) energy. All materials absorb, reflect, and emit radiant energy according to Planck's law but here, the primary concern is a special wavelength interval of radiant energy, namely thermal radiation of materials. In common ...
The template will display the table's title "Radiometry coefficients". 1 = <number> The template will display the table number as part of the table header in the following form: "Table <number>. Radiometry coefficients", where <number> is a placeholder for the number (or other table designation) given as parameter.
With the average emissivity ¯ set to unity, the effective temperature of the Earth is: = or −18.8 °C. This is the temperature of the Earth if it radiated as a perfect black body in the infrared, assuming an unchanging albedo and ignoring greenhouse effects (which can raise the surface temperature of a body above what it would be if it were ...