> -----Original Message-----
> From: Anand Dhuru [SMTP:ardhuru@VSNL.COM]
> Sent: Monday, May 19, 2003 3:16 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [OT] Material that floats in water, yet withstands heat
>
> Mike, I dont get this; I think I understand the setup you describe, but
> the
> glass tube, with or without water, would be transparent, right? how would
> you determine the presence of water at a certain point in the tube?
>
> Do you think you could share some more information about your design?
>
Think back to high school Physics lessons and total internal reflection.
The change in refractive index at the water/tube interface will cause it to
reflect all light incident on it above a certain angle.

In practice, you would need to shine the IR light into the tube at this
angle with a detector mounted adjacent at the opposite angle.


Emitter
 \
   \   _
     \| |
     /|_| tube top view
   /
 /
Detector


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