From: lewis@aera8700.mitre.org (Keith Lewis)
Newsgroups: alt.drugs
Subject: Re: Photosynthesis Philosophy.
Date: 18 Aug 92 16:06:11 GMT
Organization: The MITRE Corporation

Here are some spectral density graphs (simplified to ASCII)
from _IES Lighting Handbook_.  The *s represent broadband radiation; the |s
are single-frequency "spikes" (delta functions).

           250|            Cool White (fluorescent)
              |                        |
           200|         |           | ****
              |         |           |******
Power      150|         |           *******
(mw/10nm      |         |           *******
 /lumen)   100|      |  |          *********
              |      |  | *******************
            50|   |  |  |**********************
              |**********************************
              +------+-------+-------+-------+-------+
             300    400     500     600     700     800
               <--UV    Blue     Green     Red    IR-->
                         Wavelength (nm)



           250|         |  Daylight (fluorescent)
              |         |               
           200|         |        |        
              |         |        |  |      
Power      150|         |        |  **     
(mw/10nm      |         |    ****| ****    
 /lumen)   100|      |  |   *************    
              |      |  | ****************   
            50|   |  |**|*******************   
              |********************************  
              +------+-------+-------+-------+-------+
             300    400     500     600     700     800
               <--UV    Blue     Green     Red    IR-->
                         Wavelength (nm)



              |Incandescent Lamps (including tungsten-halogen)
              |                                      *********
              |                              *****************
Relative      |                        ***********************
Power         |                    ***************************
              |                *******************************
              |            ***********************************
              |        ***************************************
              |    *******************************************
              |***********************************************
              +------+-------+-------+-------+-------+-------+
             300    400     500     600     700     800     900
               <--UV    Blue     Green     Red    IR-->
                         Wavelength (nm)

[This is presumably for 3000 K incandesents.  Higher temperatures would
produce this same black-body radiation spectrum shifted to the left.  Of
course, you would then need UV protection.  There are fluorescents available
that simulate *only the visible portion* of 6000-7000 K black bodies.  Why
anybody would use incandescent light for growing is beyond me.]

Mercury and metal halide lamp spectrums are concentrated in a few "spikes"
distributed through the visible spectrum.  They would probably work fine for
photosynthesis.  

The low-pressure sodium is pretty much a single spike in the yellow; high
pressure sodium has spikes from green to red (not much blue).

In article <Bt5Kxv.MyD@world.std.com>, dmh@world.std.com (David M Harmon) writes:
>So where does a Halogen lamp fit in under Red/Blue/Near UV/Far UV?
Lots/little/almost none/none.

No regular lights put out significant far-UV, otherwise they would cause
skin cancer.  Far-UV lights are designed into special box-type devices (such
as EPROM erasers) for safety.

Keith Lewis             klewis@mitre.org          "Mr. Cheap"
I don't dance to music; music dances to me.  Email me for my PGP key.
The above may not (yet) represent the opinions of my employer.
Newsgroups: alt.drugs,cu.general