Re: [Phys-l] Physics Grammar

["John SOHL" <JSOHL@weber.edu>]

What John is referring to below already has a name: "the optical spectrum." That is the range of EMR that can be manipulated with transparent lenses. In the far IR the lenses are indeed unusual to most people since they are made from exotic salts. (Your skin oils and moisture will aggressively attack many of these materials. Gloves are absolutely required for handling.) 
 
Anyway, there are many creatures that can see in regions of the optical spectrum that we humans cannot. Pit viper snakes "see" deep into the IR. (Although calling that "seeing" is probably being generous.) Many insects see in either the IR and/or UV. I've done research on UV vision in anoles. (It is fun to see what they see by using a UV camera.) 
 
As John Denker pointed out, you can see into the IR if the source is bright enough. The 780nm EMR from a diode laser is readily visible, although faint. These lasers are commonly available in virtually every CD player on the market. (Looking at the same spot with an IR camera is a different story, it is *very* bright then.) 
 
In the end, I always start by explaining my terms then go from there. In this case I usually say "IR" "IR light" and/or "IR radiation" about equally. (Same for UV.) I'd rather concentrate my precious time with any particular student by working on the underlying concepts than to worry too much about this particular aspect of physics grammar.
 
John
 
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John E. Sohl, Ph.D.
Professor of Physics
Weber State University
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> > > "John M Clement" <clement@hal-pc.org> 1/23/2008 9:57 AM >>>
Of course the dividing lines in the spectrum are to some extent 
arbitrary.  But near IR, visible light, and near UV actually are 
handled by similar optical systems, while other parts of the spectum 
are handled by devices that would not look like a conventional camera. 
So calling all of these "light" is reasonable.  Or how about "light 
like".

John M. Clement
Houston, TX

> OTOH, we do tend to cut off the use of 'light' when by the time we 
> get to 
> microwaves and x-rays, so the argument then rests on the simplicity 
> of using 
> a single word term for the EM radiation--- microwave, infrared, 
> light, 
> ultra-violet, x-rays  versus  microwave, infrared light, visible 
> light, 
> ultra-violet light, and x-rays.  I suspect that neither set of 
> descriptors 
> is likely to vanish soon!