CD's as parabolic mirrors?

From: Douglas Quebbeman <>
Date: Fri Dec 8 09:49:12 2000

> I just noticed that sunlight reflecting off the top side of a CD focuses
> somewhat, maybe with a focal length of about 20 feet. Off of the data
side, it
> spreads. I've tried it with several different types, and so far they all
> the same effect. Would anyone care to explain why?

I remeber reading that a hologram of a lens would refract light in the
same was as a real lens would. This concept has formed the basis for
the flight-of-fancy holodeck/holosuite concept from Star Trek.

My guess is that (unintentionally) the spiral pattern sets up the
same interference pattern as a hologram of a parabolic mirror.

Received on Fri Dec 08 2000 - 09:49:12 GMT

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