Darren New wrote:
> Invisible wrote:
>> However, it's really damn unusual for a material's electrical or 
>> magnetic properties to have any bearing at all on its optical properties.
> 
> That's why mirrors made out of wood work so well, after all. :-)

Well, you know, there are conductive materials that are reflective, and 
ones that aren't. There are insulators that are reflective, and ones 
that aren't. There seems to be little correlation here.

>> * Iron is highly magnetic, while aluminium isn't. Good luck telling 
>> the two metals apart by their appearence!
> 
> Magnetism is a field of photons at a frequency you just can't see.

What an interesting concept...

>> * Electricity does not, under any remotely "normal" conditions, 
>> produce light or affect it in any way. (E.g., you can't bend light 
>> using electricity.) The same goes for magnetism.
> 
> Except for photoelectric effects, LEDs, solar cells, florescent light 
> bulbs, all that sort of thing.

Solar cells work by using strange chemistry rather than directly turning 
light into electricity. (Presumably that's why they're so inefficient.)

Florescent light bulbs work by stimulating atoms to release photons, not 
by directly turning electric oscilations into light.

I have no clue why LEDs work. But apparently they do. ;-)

> Don't you use a computer? What do you think you're looking at?

Electricity can be used to excite atoms in such a way that they release 
photons. So can heat energy, chemical energy, and all kinds of other 
energy. It's hardly unique to electricity. Basically if you get atoms 
excited enough, they glow.

>> (I still can't figure out why you can use an oscilator to make radio 
>> waves, but not light rays...)
> 
> You can. It just has to osscilate a lot faster.

I think I've found an answer for this one.

   frequency = velocity / wavelength

For light, the velocity varies a little, but it's roughly 300,000 km/s. 
That means that even if each wave is 1 km long (pretty damn long wave!), 
it's going to have a frequency of 300 kHz. If you make that wave 1 m 
long, that becomes 300 MHz, and by the time you get down to an utterly 
*microscopic* wavelength, you're well above the THz range.

AFAIK, nobody has ever made an oscilator that goes that fast... (Indeed, 
maybe there's even a quantum-mechanical reason why you *can't* do this? 
Don't electrons have a "frequency" after all?)

So it seems that unless you can find a material with an index of 
refraction of several thousand, you aren't going to make light with an 
electric oscilator.

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