Re: Cat's eyes

[Ludwik Kowalski <KowalskiL@MAIL.MONTCLAIR.EDU>]

John Denker wrote:

> ... I said that the cat implemented the retroreflector as a lens
> with a mirror in the focal plane.

Sorry I missed this part, a lens with a flat mirror in the focal
plane (whose normal is parallel to the lens axis) does indeed
send the beam of parallel light backward. But only when
the beam is strictly parallel to the lens axis. I do now
understand your explanation, John, but I am still puzzled
that the required conditions are actually satisfied. Yes, some
rays scattered from my face are parallel to the line between
my eyes and cat's eyes.  And yes, the cat is looking and
me while I am looking at him.

The obvious thing to try (to validate the explanation) is to
cover my face with a black mask (or to find a dark  skin
assistant ). In any case, this is an interesting phenomenon
worth discussing in a physics class. Where can one buy
two corner cubes to simulate cat's eyes? I guess a setup
made from a flat mirror and two simple lenses will work.
A good student project, I suppose. No patent is pending.


I will grab Feynman again. But I do not know if the cat
will position himself favorably again this evening. In any
case, it would be better if other people performed "cat's
eyes experiments" and shared observations. How can
Scott's observation about eye glasses can be explained?
Ludwik Kowalski