IEVref:845-01-33ID:
Language:enStatus: Obsolete
Term: geometric extent (of a beam of rays)
Synonym1:
Synonym2:
Synonym3:
Symbol: G
Definition: integral taken over the whole beam of the elementary quantity dG defined by the equivalent formulae

dG= dAcosθd A cos θ l 2 =dAcosθdΩ MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHXgaruavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiaabsgacaWGhbGaeyypa0ZaaSaaaeaacaqGKbGaamyqaiabgwSixlGacogacaGGVbGaai4CaiabeI7aXjabgwSixlaabsgaceWGbbGbauaacqGHflY1ciGGJbGaai4BaiaacohacuaH4oqCgaqbaaqaaiaadYgadaahaaWcbeqaaiaaikdaaaaaaOGaeyypa0JaaeizaiaadgeacqGHflY1ciGGJbGaai4BaiaacohacqaH4oqCcqGHflY1caqGKbGaeuyQdCfaaa@5BA2@

where dA and dA′ are the areas of two sections of an element of the beam separated by the distance l; θ and θ′ are the angles between the direction of that elementary beam and the normals to dA and dA′; dΩ= d A cos θ l 2 MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHXgaruavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaeaaciWacmGadaGadeaabaGaaqaaaOqaaiaabsgacqqHPoWvcqGH9aqpdaWcaaqaaiaabsgaceWGbbGbauaacqGHflY1ciGGJbGaai4BaiaacohacuaH4oqCgaqbaaqaaiaadYgadaahaaWcbeqaaiaaikdaaaaaaaaa@434B@ is the solid angle subtended by dA′ from a point on dA.

unit : m2 • sr

NOTE – For a beam propagating through successive non-diffusing media, the quantity G · n2, where n is the refractive index, is invariant. That quantity is called the optical extent.


Publication date:1987
Source
Replaces:
Internal notes:2017-06-02: Cleanup - Remove Attached Image 845-01-331.gif

2017-06-02: Cleanup - Remove Attached Image 845-01-332.gif
CO remarks:
TC/SC remarks:
VT remarks:
Domain1:
Domain2:
Domain3:
Domain4:
Domain5: