Re: backward ray tracing

AES <siegman@xxxxxxxxxxxx> wrote in news:siegman-3D4262.12372321022008
@nntp.stanford.edu:

In article <47BDAD4D.3060800@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Phil Hobbs <pcdh@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:


It's just what it sounds like. Ray propagation is an abstraction of
Maxwell's equations in the short-wavelength limit, and Maxwell's
equations are symmetrical with respect to time reversal.


Except that linear gain (e.g., laser gain) has to be turned into linear
loss, and v.v., on time reversal -- which can make for some interesting
and even controversial discussions when one or both are present.

Entropy?

Brian
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