Re: Pinhole camera

["Dewey Dykstra, Jr." <dykstrad@varney.idbsu.edu>]

Leigh Palmer writes:

> Roger Haar has raised an interesting point. We should treat
> the pinhole camera in our studies of physics. It is easy to
> understand, and there is lots of science in it. In my
> opinion it does no good at all to tell the student that the
> pinhole camera does not form an image. In his frame of
> reference that is manifestly untrue; it is not good science.
> It is on the same level with the statement made here in North
> America that our robins are not "true" robins, or similar
> statements which are made about our cedars and Douglas firs.
> I have an abundance of all three species in my yard, and one
> of them is 38 meters tall. Over the eighteen years I've had
> it I've noticed nothing "untrue" about it and have concluded
> that there is no useful scientific information contained in
> those statements. The definition of "image" is in an entirely
> different class: it matters in the teaching of concepts in
> physics.


> > Hi!
> >   I followed the discussion about the "image" given by a pinhole
> > camera and found it very interesting. The LEAST INTERESTING part
> > was the question about what the proper DEFINITION of "image" should
> > be.
> >    Regards    Emilio

Gee, some of us have made the nature and behavior of what one gets from a
pin hole an important feature in materials we use with students for some
time now.  We do not tell them that pinholes do not form images (contrary
to what Leigh seems to be implying).  Instead we invite the students to
carefully compare properties of real images from lenses and the patterns of
light one gets from pin holes and then we invite the students to decide
whether these are the same entities.  For some of use teaching is not
telling.

Dewey

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Dewey I. Dykstra, Jr.                   Phone: (208)385-3105
Professor of Physics                    Dept:  (208)385-3775
Department of Physics/SN318             Fax: (208)385-4330
Boise State University                  dykstrad@varney.idbsu.edu
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Boise, ID 83725-1570                       novice piper
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