So you want to know more about how light emitting diodes, LEDs, works!

Light from a Light Emitting Diode (LED) is created in much the same way
that light is created in a flourescent tube or neon sign. In an LED
crystal the electrons of its atoms are pumped up to higher energy states,
and when they fall back down again, each atom gives off a particle/wave of
light. However, the electrons in an LED are not exactly the same as the
gas molecules in a neon sign. They are not in orbitals stuck to
individual atoms. Instead the electrons occupy a contiguous "sea of
charge," and they continually wander among all the atoms in the material.
But while they do this, they maintain a particular energy level just like
they do when stuck to individual atoms. It's as if each electron in an
LED crystal was "orbiting" among all the atoms of the substance as a
whole, and the electron always "orbits" at a particular "height" above
each of the atoms it passes.

Be aware that *all* substances contain electrons. The electrons I'm
discussing here are not supplied by the battery, they instead occur
naturally in the wires, crystals, etc. They are in the LED all the time,
even when the battery is not connected. Don't make my original mistake by
imagining that electrons are injected into the LED by the power supply.
In fact, they are already in the material, and the power supply simply
forces them to flow.

Next Lesson on How LEDs work....