Re: Leds colors, just wondering...

From: martin (martin_at_123.com)
Date: 12/20/04 

Date: Mon, 20 Dec 2004 12:55:31 -0600

"John Popelish" <jpopelish@rica.net> wrote in message
news:41C705B0.F8100544@rica.net...
> John Popelish wrote:
> >
> > martin wrote:
> > >
> > > Hey Ive always wondered about the voltage as related to the colors of
LED's.
> > >
> > > Depending on the color of the Led you use a different Voltage.
> > >
> > > But what I don't understand is why? Aren't all leds the same with just
a
> > > different resin or what ever plastic surrounding it to make the color.
eg
> > > RED, or GREEN resin. I don't understand why different colors require
> > > different voltages.
> > >
> > > Can anyone answer my question ??
> > >
> > > Thanks.
> >
> > It has to do with the energy per photon. Electrons gain energy by
> > falling through the voltage across the junction, and give that energy
> > up into a photon (if you are lucky). Blue photons have about twice as
> > much energy, each, as red ones do. The junction has to be designed to
> > produce the needed drop and also to be transparent to the photons
> > produced. Each color requires a different kind of junction material
> > and structure.
>
> Of course, no simplified explanation is correct. But you might search
> Google for more details, like:
>
http://www.physics.gatech.edu/advancedlab/labs/photoelectric/photoelectric-3.html
>
>
> --
> John Popelish

Thanks John,

But if I may, so your saying that the color of the LED is not caused by the
plastic surounding the little diode device? Do they put it in a RED medium
to enhance the color.
What would happen if you put a Red "photon" inside a clear LED or can you
have a clear bright photon inside a red plastic LED.

Thanks.

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