P3D Re: light, stricly speaking....

[roberts@xxxxxxxxxxxxxxxxx (John W Roberts)]

>From: Gabriel Jacob <jacob@xxxxxxxxxxxxxx>
>Subject: P3D Re: light, stricly speaking....

>John R. writes:
>>Heat is not *any* form of electromagnetic radiation at all! :-)
>>The analogy is not useful.

>Sorry, but it is! This has been one of my points all along. 

Heat transfer may be accomplished by means of electromagnetic radiation,
and by other non-EM means such as conduction and convection. There may
also be electromagnetic radiation (of any wavelength, including IR)
with *no net heat transfer*. Heat and EM are related, but they are 
fundamentally different *kinds* of things.

>If you checked those books in the libraries you would have seen terms such
>as heat absorbing glass, heat reflecting mirrors, heat transmitting
>mirrors, radiant heat (yes RADIANT heat!), etc....., I think you
>get my point, which is, it is accepted practice to use the term heat. 

Those are all *compound terms*, which may have accepted usage not entirely
consistent with the component words. Try turning your technical dictionary 
back one page, and checking the term "heat" by itself.

>According to your logic, invisible light is a common term, 

No.

>which makes it correct. Therefore if it is a common term and accepted
>practice (not true), WHY is heat absorbing glass a misnomer? 

I didn't say it's a misnomer, and I don't think it's a misnomer. 
I think "infrared absorbing" is *more descriptive of the intended function*.

>>I actually went to a technical library to check this out...
>>There was not any note that any of these definitions was more valid than
>>the others. This is the accepted usage.

>First, I didn't see any visible light or invisible light in your above
>quotes. :-) 

I looked up the definition of "light", not the definition of "visible light".

>Secondly, the books I'm experienced with usually give preference to visible 
>radiation first, which I think is what you imply above also. 

My phone book lists Brad Aabel first, "in preference to" Joseph Zytnick.
The phone book doesn't say Brad is more correct than Joseph, and the technical
dictionary doesn't say the visible radiation definition is more correct
or preferred over the others.

>>Earlier in the debate on the definition of "light", one poster criticized
>>another for "redundancy" in the use of the term "visible light". All of the
>>technical publications I checked used the term "visible light" without shame
>>or apology, so I do not believe that earlier criticism was merited.

>Yes it was merited because "heat absorbers" was said to be a misnomer.

So one unwarranted admonition is suitable reparation for another
unwarranted admonition?

>For your information all these terms, "heat" and even "radiate" can have
>different meanings depending in the context. 

"heat: Energy in transit due to a temperature difference between the source
from which the energy is coming and a sink toward which the energy is going;
other types of energy in transit are called work"

>As for what a camera does, your analogy with the pin hole camera doesn't
>hold water! ;-) 

I made no reference to a pinhole camera. Your confusing of the terms
"pinhole camera" and "camera obscura" is characteristic of the imprecise
terminology which I said was out of place in posts in which your purpose was
to exhort others to use precise terminology.

"pinhole camera: A camera which has no lenses, but consists essentially of
a darkened box with a small hole in one side, so that an inverted image of
outside objects is projected on the opposite side where it is recorded on
photographic film."

"camera obscura: A primitive camera in which the real image of an object
can be observed or traced on the wall of the enclosure opposite the aperture,
rather than being recorded photographically" [in response to your contention
that a camera produces a real image that we see, with no reference to the
role played by the film and processing]

>The implication, because we can see IR with an IR camera makes it light

I did not make that implication - that was an earlier poster.

Definitions: McGraw-Hill Dictionary of Scientific and Technical Terms,
Fourth Edition.

John R


------------------------------