[Stoves] radiant heat capture, total heat measurement

[Kevin]

Dear Andrew

It appears to me that the inability of window glass to pass UV and IR is a 
"reflection phenomenon" rather than an "absorption phenomenon.".

Note that different coloured glasses absorb different light frequency 
ranges. For example "Red Glass" absorbs all the light in the visible 
spectrum EXCEPT for the frequencies in what our eyes tell us is "red light." 
Red glass is thus opaque to blue and green light.

Now, here is where the fun hits the fan: If red glass is transparent to red 
light, what happens to the blue and green fractions of the incident 
spectrum? Clearly, if the glass was reflective of the blue and green 
fractions, then when we viewed the glass surface from the "Incoming light 
side", the glass would appear to be blue-green, but when viewed from the 
Outgoing light side", it would appear red. "Red Glass" is thus transparent 
to Red light, absorptive of blue and green light, and reflective of UV and 
Infra red light.

Why are healthy leaves green? Very simple!!.... the Leaves are very good 
absorbers of Red and Blue spectral fractions, and very good reflectors of 
the Green spectral fraction. :-)

One thing that puzzles me is that when I went to school, in the "Olden 
Days", there were three "Primary Colors"... Red, Yellow, and Blue.Now the 
three primary colors are Red, Green, and Blue. I this progress, or what?? I 
don't think so!! How do I make Yellow if I only have Red, Green and Blue 
crayons? ;-)

Best wishes,

Kevin




----- Original Message ----- 
From: <ajheggie at gmail.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Sent: Friday, March 09, 2012 4:28 AM
Subject: Re: [Stoves] radiant heat capture, total heat measurement


> On Fri, 9 Mar 2012 03:35:06 +0000, Crispin Pemberton-Pigott wrote:
>
>>Because glass is a pretty good absorber of IR it is also a pretty good 
>>emitter.
>
> Surely glass absorbs the higher energy spectrum we can't see in the UV
> band ( which is why you won't get a tan beside a close window) and
> passes visible light and higher frequency infra red from hot bodies,
> like the sun, but absorbs the lower energy infra red from cooler
> bodies like earth and our bodies. This is the "greenhouse" effect,
> other substances act similarly but we'd best not go there.
>
> AJH
>
>
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