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Re: [Phys-l] spectra

I haven't seen their spectra myself, but a Wikipedia
( search makes me think
that the extra blue line in the fluorescent lamp is due to a particular phosphor
added to the bulb. I don't know about the shift in wavelength; can you view them
both at the same time? It could be that the diffraction grating is being bent a
little, or the viewing conditions aren't the same. And, yes, all CFLs contain a
little mercury.


"The four points of the compass be logic, knowledge, wisdom and the unknown.
Some do bow in that final direction. Others advance upon it. To bow before the
one is to lose sight of the three. I may submit to the unknown, but never to the
unknowable." ~~Roger Zelazny, in "Lord of Light"

From: Anthony Lapinski <>
Sent: Fri, October 29, 2010 5:20:59 AM
Subject: [Phys-l] spectra

I want to so a spectra activity where students look at various light
sources and gas tubes with a diffraction grating. I also have a black
light and a fluorescent light. The black light shows five distinct lines,
and matches up with mercury on my spectrum chart. The spectrum for my
fluorescent light is similar to that of the black light, but with an extra
(blue) line. Has anyone else seen this? Do CFL's also contain mercury? I
am wondering if both lights contain mercury, why are the spectral lines
slightly different?

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