# Light Theory Question



## Dryn (Sep 6, 2007)

Here is a very technical question on light theory.

Can anyone explain how much light is lost for each inch in depth? 

I have heard of the inverse square law as it applies to normal light through the air, but water being 800 times denser, how much light is lost going through the water?

For example, I would like to understand how much light is lost if the tank has, say 150 PAR at the surface (just under the water), and is 12 inches deep. I know that in such a case, there would be about 40 PAR at the bottom. How much PAR is lost per inch if I use that light on, say 6 inches of water or 16 inches of water?


----------



## Newt (Apr 1, 2004)

Without looking it up I can tell you blue light penetrates much deeper than red light. This isnt to much of a factor in the aquarium. I will rummage thru my notes and papers and see if I can find the answer and get back to you later.


----------



## Dryn (Sep 6, 2007)

Thanks Newt. I know that red light diminished at 12 inches and green light stops at 36 inches but I thought blue went on for quite a while before stopping completely (hence the blue color of deep seas). I was hoping to find out if there was any idea of how much total light diminishes per inch of depth.


----------



## Newt (Apr 1, 2004)

Knock yourself out:

http://oceansjsu.com/105d/exped_briny/13.html

http://www.punaridge.org/doc/factoids/Light/Default.htm

http://www.atmos-chem-phys-discuss.net/7/11123/2007/acpd-7-11123-2007-print.pdf


----------



## Dryn (Sep 6, 2007)

thanks... my head hurts... but if knowledge is power I should be doing good.


----------



## Zapins (Jul 28, 2004)

Here:
http://www.plantedtank.net/forums/lighting/90647-t5ho-light-intensity.html

And here, though I think you've seen this second link before:
http://www.plantedtank.net/forums/lighting/97622-par-data-selecting-t5ho-light.html

By the way, the frog you traded me is still doing well. I'm not sure how long they live, and I'm also not sure where to get him a female from for a reasonable price, but still hes living in a 10g emersed tank.


----------



## Dryn (Sep 6, 2007)

Thanks zapins. 

Its good to here that the frog is doing well. I bought him at the LFS and he got them from the reptile show in st.louis I do believe. I'm told that they hold that show every few months.


----------

