On Thursday 05 May 2005 09:07 pm, Brian Clancy wrote:
> Grant.
> Light bulbs contain inert gas at atmospheric pressure.
I was of the impression that it was at somewhat lower than atmospheric
pressure, otherwise you wouldn't get that "pop" when they break.
> Vacuum tubes (thermionic valves) contain? a vacuum.
As close as they could get to it, yeah.
> This is why the glass is so much thicker than a light bulb.
Not that much thicker, overall. I sure broke enough of them when I first
started messing around with this stuff.around with it, about 40 years or so
ago. Maybe more so if you're talking large transmitting tubes, but those
aren't exactly common.
> The most dangerous example of the devices is the large TV picture tube.
Those are rather dangerous, yeah.
> If you have a look the faceplate glass is quite thick, especially on the
> super flat screens.
The reason for that is two things -- that the outer layer of it isn't glass,
but instead is a rather thick plastic that won't shatter. Early sets had a
separate safety glass and the face of the tube was much thinner. The other
reason it's that thick is because of lead in the glass to absorb x-rays, at
least for color tubes, which is what makes TV sets and monitors a bit
"hazmat" rather than just being able to put 'em in the trash. Monochrome
monitors and old B&W tv sets don't have that issue.