It's just geometry (as is most of classical optics).
Think of the lens as a lever, or some other impedance matching device.
You trade beam diameter for beam divergence.
Another way of looking at it is that divergence is a type of error that gets magnified
by the lens as the diameter of the beam is reduced.
A small angle in a large beam gets magnified into a larger angle in the reduced beam.
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Get a free science project every week! "http://scitoys.com/newsletter.html"On Fri, Mar 30, 2012 at 4:25 PM, Nathan McCorkle <nmz787@gmail.com> wrote:
On Fri, Mar 30, 2012 at 7:16 PM, Simon Quellen Field <sfield@scitoys.com> wrote:You're now officially a badass (in a good way)... "now I know what
> I once built a megawatt UV laser with an output beam diameter of about an
> inch.
> We used a 12 inch astronomical telescope as a beam expander to limit the
> divergence, so we
> could try to hit the laser reflector that Apollo 11 left on the moon.
> Counting the photons we
> received about 3 seconds later, we got better than 80% confidence that they
> were our
> reflected photons.
you're thinking Nathan, did I fire 6 photons, or only 5?"
http://www.youtube.com/watch?v=u0-oinyjsk0
(but again, the WHY was more of what I was trying to uncover... I
don't doubt all the equations that you're recanting to me work and are
true, I want to know WHY they're true) (also some equations are only
'true' to engineers, but they aren't 'true' to scientists... e.g.
approximations)
--
Nathan McCorkle
Rochester Institute of Technology
College of Science, Biotechnology/Bioinformatics
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