Encyclopedia of Astrobiology

Living Edition
| Editors: Muriel Gargaud, William M. Irvine, Ricardo Amils, Henderson James Cleaves, Daniele Pinti, José Cernicharo Quintanilla, Michel Viso


  • Daniel Rouan
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_506-2


Emissivity is a quantity in physics that depends on wavelength and that characterizes the efficiency with which a surface radiates, compared to a black body at the same temperature. A black surface has an emissivity close to 1 and a polished reflecting surface an emissivity close to 0. Because of Kirchhoff’s law, the same quantity characterizes also the ability of a surface to absorb or to reflect impinging radiation (absorptivity = emissivity, albedo = 1 − emissivity). Emissivity is a positive, dimensionless quantity, lower than or equal to 1.

See Also


Bioorganic Chemistry Dimensionless Quantity Black Body Black Surface 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.LESIAObservatoire Paris-Site de MeudonMeudonFrance