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Dewey sez:Leigh sez:
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.
Why not ask them to compare the paterns of light one gets from a lens with
the properties of the image formed by a pinhole camera?
This is exactly one of the things that is included in what I have my
students do. (Isn't this what my sentence: "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." means to you. It's what I intended by
that sentence. Sorry if it didn't come out that way.) If you would like a
copy of the materials I use I would be glad to send them.
Are *real* images
like *real* men? They require no other explanation? How do you tell that
you are *observing* a real image?
One of the great triumphs of our species is its mastery of language. More
than any other animals we are capable of communicating sophisticated ideas
to our congeners. For some of us telling is very effective, and it is more
effective by far than "discovery" methods when approaching the more
sophisticated ideas of physics. I consider optical imaging phenomena to be
sufficiently sophisticated that considerable didactic elucidation of their
details is appropriate. Of course some practical work is necessary, but in
my experience students don't learn without both components. This isn't
either.relativistic quantum mechanics, but it's not easy for the beginner
As I turns out I find that "considerable didactic elucidation of their
details" is not necessary. (...making "didactic elucidation" a kind of
oxymoron for me...)