[ATM] mirror or lens?

[Mike Shuken <mikeshuken@value.net>]

Hello,

I was at a family lunch the other day and I was telling the folks about a 
reflector telescope that my son and I just built.  Most of the family is 
from a non-technical background, and one of them asked "How big is the lens?"

I said, "Well, it's not really a lens, it's a series of two mirrors, and 
the eye piece is really the only *lens* in the telescope."

And one of the family members said, "A mirror is still a lens."  And he's 
an astrophysicist, and who really wants to argue with an 
astrophysicist?  So I didn't knwo what to say.

Anyway, I always thought that a mirror wasn't a lens, a lens was something 
that light passed through and was changed, vs. a mirror that changed the 
light by reflected it.

Any thoughts on weather a mirror is a lens?

Best,

Mike


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