# light, photons, irradiance. Adding it all up help.



## kadimkris (Sep 19, 2011)

So I'm not too sure what I'm doing here. I what to know how many photons there are in the given wavelength of "light". I have been digging for about two weeks in spare time. I am learning about plants and lighting and trying to make a project to build a light tailored to plants needs. At the moment I need to find out how to get total about of photons that are produced by a given light.

Terms I know "of":
mole (unit)
einstein ( unit)
Irradiance 
"PAR"and "PUR"
plus some others
I have some background in electronics and engineering as this is what i am going to school for. just two days ago I learned the differences between optics for the human eye and measurements and true power are different . lumens, candle, etc vs photons etc. I am wanting to learn more about light and need steered in the right direction .
the issue at hand is that spec sheets have ton of info but most are geared towared the human eye can we take the info they give use and come up with irradiance in photos or einsteins. As i learn about botany (hobby) I have learned they have done test to show that this is the max amount of light a plant can use in this wavelength. 
sorry for the long post and thanks for your time. here is a sample of a few lights i am looking at atm.


cree xlam xr-c

spec sheet http://www.cree.com/products/pdf/XLampXR-C.pdf

royal blue
wavelength range 450-465
min radiant flux 300 mW (+/- 7%)
350mA @ 3.6 volts dc ( this = .35*3.6= 1.225 watts )

red
wavelenght 620-630
luminous flux 39.8 lm (+/- 7%)
700 mA @ 2.4 volts dc ( this = .7*2.4= 1.68 watts )


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## Ken_McE (Sep 19, 2011)

kadimkris said:


> I (want) to know how many photons there are in the given wavelength of "light".



Would vary with brightness, no?


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## StarHalo (Sep 19, 2011)

These are some extremely precise plants that require an exact amount of photon energy..

And you're nowhere near the big question, which has nothing to do with the quantity of light, but rather how to pay for the power needed to generate it..


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