>Many substances fluoresce under UV light. Are there any
>which do so under IR or are the energy levels all wrong ?
>I think short wavelength UV is converted to longer wave-
>length visible light by the fluorescee and IR is longer than
>visible. Just wondering if there's some quirk of nature/
>physics that would make it possible to use invisible flood-
>lighting

I have a little IR tester which consists of a piece of FR4 fibreglass sheet
with a dob of what looks like epoxy on the end. If you shine IR at it glows.
Its reaction is sufficient to use it to verify that a typical remote control
is illuminating its LED. I do not know what the epoxy is, but it appears to
be a test tool made by Kodak, I suspect for engineers to test IR sensors in
machines.

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