From: SFPhysics@aol.com
Date: Sun Aug 22 2004 - 01:44:47 PDT
From: SFPhysics@aol.com Message-ID: <d4.14979e54.2e59b6ff@aol.com> Date: Sun, 22 Aug 2004 04:44:47 EDT Subject: Discharge Spectrum Tubes...
Does anyone know of a location where I could borrow a discharge tube
& power source for a week to show my chemistry students? (I don't
have the budget to buy one for my class, but I'd really like to show
students the emissions spectra of an element or two.)
~ Geoff
Dear Geoff:
Your students can see emission spectrum lines from less costly sources. Neon
discharge lamps that are sold for fake electric candles yield a very nice
spectrum even with the $5 diffraction grating spectroscopes sold by supply
houses. Smaller Neon lamps can be connected to AC line voltage with a 22 KOhm
resistor for a total cost less than one dollar. You can also put table salt into a
flame to do Sodium lines and other metallic salts like Strontium are
spectacular. A clear glass UV "bug" lamp will have nice Argon and Mercury lines but
care must be taken to avoid long exposure of the eyes to the UV. The same
warnings go for "sun" lamps used in tanning. Cheap "psychedelic" plasma displays
can be had for as little as $20. The "glowing dolphin" has good Nitrogen and
Oxygen lines. None of these are as bright as the concentrated capillary
discharge tubes but then they aren't $600 either. One bright source would be the
new "blue light" headlamps found in upscale autos. These short arc discharge
lamps have several gases with very bright lines, Krypton and Xenon mostly. The
bright Mercury vapor/Xenon lamps in many school gymnasiums provide yet another
viewable source. Besides Sol there are gas plasmas found all around us.
Unfortunately few are pure enough to give a single element spectra. Too bad you
cannot do a class at night where you can see Sodium and Mercury vapor street
lamps but you could hand out a couple of the $5 spectroscopes for students to
take home and use after dark.
Hope my suggestions may help, best wishes to the list,
Al Sefl
Who has more lines in his old face than Fraunhofer could find on the sun...
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