On Jan 14, 2013, at 10:14 AM, Roger Furer wrote:

> They definitely put out UV. I visited a salt water aquarium shop and I co=
mmented on the fluorescence of the corals and some fish.

Oh come on.  They measure this stuff.  Blue LEDs have a very narrow output =
frequency range, and it doesn't include any "UV."  However, blue light is a=
lso quite capable of causing some dyes to fluoresce, and presumably can cau=
se fading in pigments.  It's not like there's some magical property of "UV"=
 (the definition of which is based on human vision); you have a more-or-les=
s (quantum exceptions) spectrum and the UV is right next to the violet and =
that's just next to the blue.  To cause fluorescence or pigment damage, all=
 you have to have is a photon whose energy is sufficient (wavelength small =
enough) to trigger some electron state transition in a molecule somewhere.

This article implies that the standard excitation frequency for various sci=
entific purposes is down around 488nm (Argon ion laser; a pretty monochroma=
tic source), which is sort-of blue green.  It also has nice explanations of=
 the phenomena in general, and bleaching.
http://www.invitrogen.com/site/us/en/home/References/Molecular-Probes-The-H=
andbook/Introduction-to-Fluorescence-Techniques.html


--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.