Re: Heat vs IR

[boblong@xxxxxxxxxxx (Robert Long)]

On Tue, 26 Nov 1996 01:11:56 +0000 (GMT), you wrote:

|Having read the article on WJM's web page can somebody clarify the=20
|wavelengths of heat as we know it.
|
|HIE has an extension of sensitivity to IR to about 1000nm which is =
further=20
|than that of SFX200, Konica 750nm etc.
|What are the wavelengths of near and far IR (heat)??

Admittedly a very confusing subject.  The wavelengths that are used to
"melt" the metallic layer in CD-R blanks and so on presently are right
in the range of near infrared and extreme red we are using to take
pictures with HIE.  And the wavelengths are growing ever shorter as
alternative laser sources become cost-effective.  The explanation I
got from an engineer for this apparent anomaly was that human beings
equate far infrared with heat because we feel the far infrared--but
not shorter wavelengths--as heat.  But metals "feel" the entire
spectrum as heat, so wavelengths that won't warm us will melt the
metallic layer for long enough to create "data pits" in the CD-R
blank.

Many years ago, some magazine--I think it was Vogue, though I can't
imagine my mother buying Vogue--had a special issue devoted to the
future.  In it was a fiction piece about a couple in their
up-to-the-minute apartment who decide to have a dinner party on the
balcony in midwinter because the radiant heating (at that time, the
dernier cri) makes it so comfortable.  In the event, the butter melts
in the dish because it absorbs as heat too much of the IR, while the
water freezes in the glasses because most of the IR passes right
through.

So what is "heat"?

Bob Long
(boblong@xxxxxxxxxxx)

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Topic No. 5