Re: [ATM] Card in the foucault test

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

Everyone? Hmmmmm. 
Actually, I have never seen any advice on using a
card, only on using a knife-edge. This is an
interesting question, and I think Ken was being a
little too prickly in his dismissal of the question,
even though the advice to read Dave Harbour's article
is good advice. (Though you won't find the exact
answer to your question in there, David!) Am I correct
in thinking that you are using a pinhole as a light
source instead of a slit? Most folks use a slit
instead; but you have to make sure that your
knife-edge and your slit are quite parallel indeed.
Have fun.
Guy

--- Ken Hunter <atm_ken_hunter@yahoo.com> wrote:

> Everyone on the list knows why it's doing this
> except
> maybe you... You will need to read up on the
> Foucault
> test. An excellent read is David Harbour's
> description
> of exactly what you are seeing and why it's
> happening.
> 
> As an exercise, I suggest that you read this FIRST
> and
> then come back to ask your questions. You will save
> us
> and yourself a lot of time if you do the homework
> first.
> 
> www.atmsite.org/contrib/Harbour/Foucault.html 
> 
> Ken Hunter
> 
> 
> --- David  Williams <dwilliams1128@earthlink.net>
> wrote:
> 
> > Hello
> > 
> > I have taken the lists advice about using the card
> > to cut the cone of light returning from the mirror
> > in the foucault test.  The only thing is, that
> > instead of using a card or playing card, I'm using
> a
> > piece of paper like a piece of dot matrix paper. 
> > This has produced an interesting effect.  I can
> see
> > the cone of light to a pin hole like area if I
> hold
> > it right.  And while I have the paper at this area
> > and the knife inside the ROC and move the knife to
> > the left, the image on the paper moves to the
> right.
> >  Does this mean that the knife is out side the ROC
> > or the paper is outside the ROC?  Also when I move
> > the paper back to get the image to where the it's
> > not a point anymore, the image looks like a donut
> > like this:
> > 
> >                      _______
> >                   /              \
> >                 /   /              \ 
> >              /    /                    \ 
> >             |    |                        | 
> >             |    |                         | 
> >              \   \                         /
> >                 \  \                      / 
> >                     \  \ _____  _  /
> >                          
> > 
> > 
> > 
> > So it looks like a cresant moon on the left hand
> > side.  Does any one know why it's doing this?
> > 
> > Thanks
> > David
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> > 
> 
> 
> 
> 	
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=====
Guy  Brandenburg
Washington, DC
My home page:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
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