Re: halogen bulbs

[Leigh Palmer <palmer@sfu.ca>]

> On Thu, 9 Apr 1998, David Dockstader wrote:
> > For those of you who know about light bulbs, what's the deal with halogen?
> > I can see why a Xenon filled bulb would be good but halogen?
>
> I asked the same question a few months back and was told the following...
>
> When a filament gets as hot as those in high intensity bulbs, some of the
> metal from the filament vaporizes into the bulb.  The halogens react with
> these vaporized particles from the filament and redeposits them back on
> the filament.  This extends the life of the bulb.

I'll add a little to that, but I don't have an authoritative source.
All of what was said conforms to what I was told, and in addition I
was told that the tungsten is redeposited preferentially at the
hottest spots in this reaction. That seems highly counterintuitive
to me, but my physical intuition tells me that I should not take my
physical intuition too seriously!

Leigh