Encyclopedia of Astrobiology

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


  • Sylvia Ekström
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_1109-3


Opacity measures the property of a medium to attenuate light. The opacity depends on the composition of the medium, its density, and temperature, but also on the wavelength considered. The absorption coefficient aν (with units [cm−1]) enters into the definition of the optical depth. More often in astronomy, it is the mass absorption coefficient \( {\kappa}_{\nu }={a}_{\nu }/\rho \)


Absorption Coefficient Essential Role Bioorganic Chemistry Free Path Electronic Transition 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Observatoire astronomique de l’Université de Genève, Faculté des SciencesUniversité de GenèveVersoixSwitzerland