Re: xenon/noble gases/white light, etc.

["faust" <faust@gateway.net>]

>
> You can get bulbs from PIAA and probably just about
> every other european bulb manufacturer than have xenon or some such gas
> inside the bulb.  There's no coating, like on those cheap
blue/yellow/green
> lights you see on the rice cars.  They wont' fool anyone into believing
you
> have real HIDs but they do emit a bluer light than normal halogens.
> 
> BTW you can also get bulbs that emit whiter light by using filaments that
> "glow" at a higher temperature.  

The function of the gases in the envelope of an incandescent lamp is to
prohibit the burning of the filament.  In a "halogen" lamp, the envelope is
filled with a halogen gas (usually bromide).  When you turn the lamp on,
instead of the filament burning up slowly, the heated particles of tungsten
react with the halogen gases in such a way that causes them to be
re-attracted to the filament.  This is known as the Tungsten-Halogen
Regenerative process.  What this means is that lamps with normal filaments
will last longer than normal.  Most household standard incandescent lamps
fail because of the filament has burned so much tungsten that it will no
longer conduct.  With a T-H lamp, the filament lasts longer, so it will can
resist more current flow, while still conducting electricity.  This
increased capacity to provide resistance is what allows the T-H lamp to
burn brighter.  

The gases in the lamp should not affect the "color" of the light, except
that they may allow the filament to burn hotter, producing a light of
higher color temperature.  But, the color temperature of an incandescent
lamp is very limited.  Nobody has been able to develope an incandescent
lamp that produces light close to "white light".
I suspect that most of the "hyper-white" and "UV" lights appear whiter
because the lense has a dichroic filter coating on the envelope that
specifically prohibits certain visible wavelengths of the electromagnetic
spectrum to enhance the appearance of non-visible wavelengths (UV).  All
light sources contain some amount of UV.  Keep in mind that most UV rays
are non-visible; ie, they won't affect your abiliy to see at night.  The
lamps could be filtered to color-correct, or artificially increase their
color temperature by enchance wavelengths in the blue and violet range.

I shouln't drink so much coffee late at night.

later,
Greg Faust

85 Mazda RX7 - dedicated autoxer
86 Jetta Deluxe 2dr - dedicated snow dog
87 GLi  - dedicated baby carrier
88 Scirocco 16v -dedicated to me (206k miles and counting)

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