emissividad
Emissivity is a property of a material or surface that describes its efficiency in emitting thermal radiation compared with a perfect blackbody at the same temperature. It is defined as the ratio of the spectral or total radiant exitance of the surface to that of a blackbody, with values between 0 and 1. Emissivity can depend on wavelength (spectral emissivity), direction (angle of emission), and temperature, and real materials are often non-grey, meaning ε varies with wavelength.
For opaque bodies that do not transmit radiation, absorptivity equals the complement of reflectivity; Kirchhoff's law
In radiative heat transfer, the total emissive power of a surface is M = ε σ T^4 if treated
Measurement and selection: Emissivity is influenced by surface roughness, coatings, oxidation, and temperature. It can be
Applications include designing thermal insulation and coatings for solar collectors, furnace linings, and heat exchangers; in