jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>
>>> actually, /all/ semicons emit light when they conduct, you just don't
>>> usually get to see it because of the casing. and it's usually in the
>>> infra-red spectrum.
>>
>> I'm afraid you're quite wrong.
>
> no, i'm quite right. re-read my post. "light" isn't just visible.
>
>>
>> http://en.wikipedia.org/wiki/Led :
>>
>> "The wavelength of the light emitted, and therefore its colour,
>> depends on the band gap energy of the materials forming the p-n
>> junction. In silicon or germanium diodes, the electrons and holes
>> recombine by a non-radiative transition which produces no optical
>
> note: OPTICAL.
>
>> emission, because these are indirect band gap materials. The materials
>> used for an LED have a direct band gap with energies corresponding to
>> near-infrared, visible or near-ultraviolet light."
>
> that's why i said infra-red. normal semiconductors emit in infra-red.
> with chemistry, you can tune the band gap to optical energies, and thus
> get visible emissions. but you don't do that for standard semicons!
> look up the band gap energies and correlate them to emission spectrum.
Hey, guys....
Heat is infra-red. Extremely infra-red becomes ultra high frequency
radio waves. The different colors of LEDs are due to the band-gap
energies involved in the chemical cocktail used to make the LED.
Each blend puts out light in a very narrow, almost spike, wavelength.
Red is around 750nM and Blue near UV is around 400nM, or 0.4 microns.
The human eye (retina) can detect down to 300nM but the lens cuts out
the light up to about 400nM. I didn't look this up, but Isaac Asimov
mentioned that a friend had cataract surgery and could see shades of
purple that others could only imagine. It was in the preface of one of
his sci-fi books around 1960. He was not only a writer but a real
professor, so I think that one would prove to be true. Finding a
reference might be a bit rough, but the Opthalmology association should
mention it somewhere.
Super high frequency radio == infra-red.
Super infra-red == ultra UHF radio.
Simple?
Bill Baka