optical depth

 

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optical depth

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optical depth (countable and uncountable, plural optical depths)

1. (physics) The natural logarithm of the ratio of amount of radiation that hits an object to the amount of radiation that emerges from that object on the other side.

   Synonym: optical thickness

   • 2006 August, Alexander V. Krivov, Artem G. Feofilov, Valeri V. Dikarev, “Search for the putative dust belts of Mars: The late 2007 opportunity”, in Planetary and Space Science, volume 54, numbers 9–10, →DOI, page 871:

     The previous attempt of direct observational detection, undertaken with the Hubble Space Telescope (HST) during the Mars equatorial plane crossing in May 2001, set an upper limit on the normal optical depth to ${\displaystyle \sim 3\times 10^{-8}}$  for the Phobos ring and ${\displaystyle \sim 10^{-7}}$  for the Deimos torus.