cie

17-21-048

optical extent

etendue

product of geometric extent and the squared refractive index of a medium through which the beam propagates

Note 1 to entry: The optical extent is invariant and remains constant when the beam is propagating through successive non-diffusing media.

Note 2 to entry: See also "geometric extent".

Note 3 to entry: The optical extent is expressed in square metre times steradian (m2·sr).

Note 4 to entry: This entry was numbered 17-845 in CIE S 017:2011.

Publication date: 2020-12
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