Re: [Phys-l] Galileo was wrong

["John Clement" <clement@hal-pc.org>]

In the near field, I was referring to an object close to a magnifying glass.
So different parts at different distances would have different virtual
magnifications.  Actually in the near field with a small object you can see
the back side of an object, something that I learned fairly recently.

Yes he could have verified constant magnification, and I would have been
surprised if he had not.

Incidentally I saw HS seniors laying a magnifying glass flat on an object to
look at it.  I had to tell them to move it away to magnify it.  Obviously
they didn't understand how to use them.  Eventually I gave up and gave them
bug boxes setup to create the correct distance.  Haven't they ever used a
magnifying glass?

John M. Clement
Houston, TX

> I'm evidently stupid or misinformed, as I would write different parts of
> the object produce different sizes in the image.  Also I thought near and
> far field referred to the inverse square law where it fails near the
> object or antenna.  Generally this is within a distance of approximately
> the size of the antenna.
>
> Another definition is at far field the diffraction pattern differs little
> w/ that at infinity.  W/ a microscope a I can envision inconstancy, but
> not a telescope.
>
> bc
>
>
> p.s.  Galileo coulda verified that at least on the earth his telescope had
> constant magnification by using objects scaled according to their distance
> appeared (obscured each other) equal(ly).
>
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> On 2010, Sep 25, , at 12:24, John Clement wrote:
>
> > Looking at the article in the TPT the author is trying to
> > make the case that the magnification of a lens is consistent.  But that
> is
> > not completely true when you consider the situation of something in the
> near
> > field where the magnification varies for different parts of a 3D object.