OD, Soaked Rice, and Black Cultures

Today I Learned:
1) OD, or optical density, the measurement used by biologists to measure the density of bacterial cells in suspended culture, is actually a log scale. Specifically, an OD at a wavelength is the negative base-10 logarithm of the ratio of the amount of outgoing light at that wavelength to the amount of incoming light at that wavelength. This is... disquieting, because OD is usually assumed to vary linearly with cell density. If, however, OD is a log measure, then it should vary as the *log* of cell density, which means a linear increase in OD is actually an exponential increase in cell density. Can anyone out there clear this up?

EDIT: A reader pointed out to me that it actually makes a ton of sense for a log measure of light getting through to vary linearly with cell density. If there's one particle of bacteria in your solution, it absorbs some fraction F of of the light coming in. If you add a second, it absorbs F of the F that got through the first one, so the remaining light is F^2, etc, so the fraction of light getting through with N particles is F^N. Therefore log(F^N) ~ the number of particles.

2) Rice can be kept warm in the water it's going to be cooked in before it's cooked for a surprisingly long time apparently without affecting the end result.

3) Certain kinds of bacterial culture turn startlingly *black* when bleached. And it's not because of the phosphate buffer we used. *shrug*.