Re: My Optics Education Project (MOEP)

["Paul Camp" <pjcamp@coastal.edu>]

> Specifically, I doubt that from everyday life experiences one would
> generate the notion that three special rays are what create a point on an
> image.  Yet, this notion is so clearly present that many _teachers_
> expressly use it to make predictions about what will happen if one covers
> half a lens.  I have even had groups of teachers suggest that if one were
> to cover portions of the lens at the top, middle, and bottom edges of a
> lens that the image of the top of the object would not be visible.  (Think
> about it.  Where to the three principal rays intersect the lens?)

> Dewey
>
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> Dewey I. Dykstra, Jr.                   

Which makes these experiments worth getting the students to try. 
There is also a related notion that an image does not exist unless 
there is a screen to view it upon (this despite what you may have 
done regarding virtual images -- these are always viewed not as an 
image but as the object itself in some sense). So it is also worth 
taking the screen away and getting the student to stand some distance 
beyond the lens to view the image hanging in space. Then things like 
telescopes and microscopes begin to make a great deal more sense.

Paul J. Camp                   "The Beauty of the Universe
Assistant Professor of Physics  consists not only of unity
Coastal Carolina University     in variety but also of 
Conway, SC   29526              variety in unity.
pjcamp@csd1.coastal.edu             --Umberto Eco
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