From:	Marc Renouf <renouf@********.COM>
Subject:	Re: thermographic vision-question
Date:	Tue, 2 Feb 1999 19:52:10 -0500

On Tue, 2 Feb 1999, David Woods wrote:

> Really? Irrc the transmission of most glasses drops quite rapidly
> <400nm. I would have thought that most objects, opaque in the visible,
> would be opaque in the UV range. Unless you know different.

Transmission of UV drops off pretty quickly. Typically, if you're
doing anything with UV you need quartz or fused silica lenses. The only
reason I know this shit is because I was working on constructing a UV
Lidar for work. What a pain in my ass. "Yes, we need a huge-ass
telescope, and by the way it needs a Schmidt corrector plate that runs all
the way down to 308 nm." At which point the telescope guy says, "Okay,
but it's gonna cost ya." Trust me, this is something you *never* want to
hear from an optics supplier.

> As for Sonar, I can't imagine solid objects being transparent to sound
> waves. Although, admittedly it's not my field.

Your gut instinct is right. Glass is opaque to ultrasound.

Marc