RE: [AGA Member] Light in deep tanks

[Livay Aviel-R51374 <Aviel.Livay@motorola.com>]

Hi,

Hi,
There are some factors that we need to take into account for answering your question, actuall Scott mentioned pretty much most of them -I would like to point out one factor that we should *not* take into account - and I would like a feedback for that from this distinguished community.

I am referring to the attenuation of light as it deeps through the water.

My understanding is that once light crosses the surface it behaves according to the beer-lambert law:

http://www.shu.ac.uk/schools/sci/chem/tutorials/molspec/beers1.htm

P=P0 * e ^(-ebc)

Where 
P is the intensity 
P0 is the intensity at the water surface
e is the molar absorbtivity with units of L mol-1 cm-1
b is the path length of the sample - that is, the path length of the cuvette in which the sample is contained. We will express this measurement in centimetres.
c is the concentration of the compound in solution, expressed in mol L-1

So - yes - the light intensity is decreased exponentially as we go deepr,

But what is the factor?

My best reference so far is figure 6 in this paper

http://www.aquabotanic.com/paper2-6.html

It shows that for pure H2O after one meter:
400-50 nm - almost no absorption.
600 nm - 20% absorpion
700 nm - 40% absorption

This is after 100 cm - our tanks are 40-60 cm deep - right?

Now when Karen is describing the amazon water then it's a different story - If I understand correctly - it is either deeper or browner...

So depth isn't such a big factor putting aside reflections, shading, etc.

Now one favor - in order to close this issue once and for all - has any one came across a table that describes the Beer coefficients for water and other substances in various wavelengths? I really need it badly... :-)

Thanks,

Aviel.

-----Original Message-----
From: owner-aga-member@thekrib.com [mailto:owner-aga-member@thekrib.com] On Behalf Of Amit Brucker
Sent: Thursday, April 08, 2004 9:51 PM
To: aga
Subject: [AGA Member] Light in deep tanks

Hi All,
Does any one know or have researched how effective are fluorescent lights in deep tanks (Over 60cm) ???
What would be the percentage of light loss in the deeper areas of the tank ?
Thank you,

Amit brucker
www.plantica.com




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