In article , Richard J Kinch
says...

Phosphor? In an LED?

Yes. The white LEDs that radio shack
sells are really blue led's that excite
a bit of yellowish phosphor on top
of the diode. They have the same
turnon voltage as the blue ones, and
a close inspection of the light
shows that the lens focusses the
blue and yellow light at a slightly
different spot.

Sort of a 'cool white' effect. The
human eye sees blue and yellow light,
and says 'hey, that's white!'

Jim

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