Date: Mon, 29 Sep 1997 11:02:16 +0100 From: "Tim Williams" <Tim@jint.jasco.co.jp> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg3759$foo@default> Subject: Hard radiation!
Paul Burkhardt wrote:
"How about gamma rays, x-rays, microwaves, ultraviolet, infrared, and radio
waves? Which would fall into your warm spectrum, and which into your cool
spectrum? They are all electromagnetic waves, that is, components of the
full spectrum of light which are emitted from our sun and universe, and
play very important roles in molecular processes. Artificial lights also
emit these non-color wavelengths to certain extents, so how do you know
that the 'cool' part helps with compact leaf growth, and the 'warm' part
helps with flowering without considering these invisible wavelengths?
Paul Burkhardt"
Paul, this is true up to a point, but fortunately for us our commonly
available light sources do not emit much above the near UV (just outside the
visible), and in fact very little of that. To get much UV and "harder"
radiation requires much higher temperatures or else quite different emission
processes, hence although our sun emits X-ray, to get the same wavelengths
on earth requires X-ray tubes (which do not operate on the same principle as
flurorescent lamps) or other more complex machines like synchrotrons!
Likewise, radio- and micro-waves can be neglected; although part of the same
electromagnetic spectrum, their generation processes are again different.
The high end of the spectrum in all lamps is cut off at some point, but the
lower end is more extensive. Commercial "domestic" lamps of all sorts do
emit IR (=heat) as well as a broad spectrum of visible wavelengths, but
outside the visible only filament lamps generate much and it's all in the
IR, a good reason to not use these for growing plants. I don't think
(although I could well be wrong) that having a lot of UV outside the safe,
near-UV visible to insects and the like, would be good for our plants, as it
would probably do to them what the ozone-hole induced UV is doing to people
who expose their skin to too much southern-hemisphere sun. I also suspect
that commercial high-intensity agricultural lamps should be treated with
some caution, as they DO generate UV in sufficient quantities to pose a
health risk if they are too close to our skin or eyes.
Best regards,
Tim Williams.
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