# light intensity vs. distance

```Hi again, still planning my new setups (thanks to everyone for all of the
help and suggestions I've received up to this point). Does anyone know the
equation for light intensity as a function of distance through a medium?
I'm trying to figure out if the light intensity at the bottom of a half
empty tank == the light intensity at the bottom of a full tank of the same
height. I seem to vaguely remember from college physics that light
transmission though air is faster (and presumably better) than through
water. However, the water surface would be reflective at a distance so...

Point being, I'm going to have a half full tank and want to know how much
light to put over it (assuming Anubias, Nymphaea, Ceratopteris, and
Eleaocharis (I'm planning a West African theme)). However, my fiance'
informs me that I am a "fish geek," and as such, would prefer the
mathematical equation to calculate these things for myself to a simple

Thank you in advance,(I was gonna use a semi-colon here, but my fiance'
informs me that this would make me a computer geek as well :)

Jason F. Smith
Center for Cognitive Neuroscience
Department of Neurology
Temple University School of Medicine
Cancer Center, Suite 200
3322 N. Broad St