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Re: PHYS-L digest 425

On Fri, 30 May 1997, brian whatcott wrote:

At 07:10 5/29/97 -0700, William Beaty wrote:
...
Lenses are essentially smoothly-joined arrays of microscopic prisms. It
is possible to combine two lenses, one of them "upside-down" (one concave
and the other convex), so that the composite focal length is less than
that of just one lens, but the frequency-dispersion effects are
minimized. The result is the "color corrected" lens.

Nice exposition. I think you meant the composite focal length is longer
for an achromat

Oops! Right, I was thinking "ability to deflect light" but wrote "focal
length"

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