Template:Radiometry coefficients

Radiometry coefficients

Quantity		SI units	Notes
Name	Sym.
Hemispherical emissivity	ε	—	Radiant exitance of a surface, divided by that of a black body at the same temperature as that surface.
Spectral hemispherical emissivity	εν  or ελ	—	Spectral exitance of a surface, divided by that of a black body at the same temperature as that surface.
Directional emissivity	εΩ	—	Radiance emitted by a surface, divided by that emitted by a black body at the same temperature as that surface.
Spectral directional emissivity	εΩ,ν  or εΩ,λ	—	Spectral radiance emitted by a surface, divided by that of a black body at the same temperature as that surface.
Hemispherical absorptance	A	—	Radiant flux absorbed by a surface, divided by that received by that surface. This should not be confused with "absorbance".
Spectral hemispherical absorptance	Aν  or Aλ	—	Spectral flux absorbed by a surface, divided by that received by that surface. This should not be confused with "spectral absorbance".
Directional absorptance	AΩ	—	Radiance absorbed by a surface, divided by the radiance incident onto that surface. This should not be confused with "absorbance".
Spectral directional absorptance	AΩ,ν  or AΩ,λ	—	Spectral radiance absorbed by a surface, divided by the spectral radiance incident onto that surface. This should not be confused with "spectral absorbance".
Hemispherical reflectance	R	—	Radiant flux reflected by a surface, divided by that received by that surface.
Spectral hemispherical reflectance	Rν  or Rλ	—	Spectral flux reflected by a surface, divided by that received by that surface.
Directional reflectance	RΩ	—	Radiance reflected by a surface, divided by that received by that surface.
Spectral directional reflectance	RΩ,ν  or RΩ,λ	—	Spectral radiance reflected by a surface, divided by that received by that surface.
Hemispherical transmittance	T	—	Radiant flux transmitted by a surface, divided by that received by that surface.
Spectral hemispherical transmittance	Tν  or Tλ	—	Spectral flux transmitted by a surface, divided by that received by that surface.
Directional transmittance	TΩ	—	Radiance transmitted by a surface, divided by that received by that surface.
Spectral directional transmittance	TΩ,ν  or TΩ,λ	—	Spectral radiance transmitted by a surface, divided by that received by that surface.
Hemispherical attenuation coefficient	μ	m−1	Radiant flux absorbed and scattered by a volume per unit length, divided by that received by that volume.
Spectral hemispherical attenuation coefficient	μν  or μλ	m−1	Spectral radiant flux absorbed and scattered by a volume per unit length, divided by that received by that volume.
Directional attenuation coefficient	μΩ	m−1	Radiance absorbed and scattered by a volume per unit length, divided by that received by that volume.
Spectral directional attenuation coefficient	μΩ,ν  or μΩ,λ	m−1	Spectral radiance absorbed and scattered by a volume per unit length, divided by that received by that volume.