Note:

This article:

http://en.wikipedia.org/wiki/Exponential_decay

Says:

Quote - The intensity of electromagnetic radiation such as light or X-rays or gamma rays in an absorbent medium, follows an exponential decrease with distance into the absorbing medium.

I was glad to see that. I had calculated from first principles that light had to work this way, but I wasn't sure. But if Wiki says that's how it works, I'm going to assume I did it right.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)