RE: Re[3]: Zenon bulbs?

["Cooley, Christopher" <Christopher.Cooley@bactc.com>]

Just wanted to say thanks to Brian for an OUTSTANDING explanation on
Xenon bulbs in a technical yet understandable fashion.


	-----Original Message-----
	From:	Brian Gracek [SMTP:bgracek@cloudnet.com]
	Sent:	Friday, May 29, 1998 1:52 PM
	To:	jettaglx@igtc.COM
	Subject:	Re[3]: Zenon bulbs?

	>wow brian...i dont wanna sound lame...but can you explain this
again so i
	>can understand it..8)
	>i use to drive a honda...so i am a little slow with things..
	>geo
	>-----Original Message-----

	Sure I'll try...

	The halogen bulbs we all use are made with a tungsten filament
(little coil
	of wire inside the bulb), the bulb is the evacuated (all the air
sucked
	out), then a halogen gas is placed in the bulb.

	The halogen gas glows when heated by the filament...while the
bulb is what
	we would call hot (it will burn you), in the world of lighting
it isn't
	very hot so the color we see is yellowish.

	The HID (high intesity discharge) lamps we see in the expensive
cars
	described (Porsche etc) in a gap between two high voltage
electrodes.  The
	Xenon gas is different from a halogen gas (I won't go into
quantum
	mechanics and molecular orbnital theory here...just know that
they work
	differently) in it will emit a whiter light when heated to a
higher temp
	(the halogen gas would decompose and ionize at these temps and
be useless).

	The big lesson here is temperature is DIRECTLY related to color
output.
	Let me give an example that I used to use on audiences when I
worked in a
	planetarum.  Think of a blacksmith working on an iron
bar...removing the
	bar from the hot coals shows the bar glowing red, the bar is hot
but is
	relatively cool on a temperature scale that applies to a star,
so red is a
	"cool" color.  Now imagine we can make the fire hotter and heat
the bar
	some more...remove the bar and it glows yellow (like our sun) at
this point
	the bar is molten actually...if we heat the bar some more it
glows white
	(i.e. white hot)  at this point the bar is actually boiling!
If we could
	heat the bar even more it would glow blue...and heating even
more and only
	UV is emitted...

	so, the bluer, the hotter the gas is in the bulb...the redder,
the cooler
	the bulb.  Remember the rainbow?  ROY-G-BIV... IR then, Red,
Orange Yellow,
	Green, Blue, Indigo, Violet...then UV
	so it goes on the energy spectrum...red light is a low energy
photon violet
	is a high energy one...and UV enven more, that is why people
worry about UV
	radiation (light)...it is higly energetic and can damage
cells...

	So the differences are in the gas and the temperature.

	So, why add Xenon to a halogen lamp...well it MAY provide some
help, even
	though the temps are a bit cool, population probability tells us
some (very
	few) atoms will be in the ulrta excited state...if some xenon
atoms are
	excited then we may get a small bump in output...BUT

	it is the same calculations that show nearly every xenon atom
will be in
	the excited state at a higher temp which is only available
without a
	filament and within an arc!  So they designed a HID.

	***********************************************************
	Brian "Jetta TREK" Gracek		    Saint Cloud,
Minnesota, USA

	"On the road of life"...There are 'windshields', and there are
'bugs'
			          (splat!)

			"Squeegees Wanted"