Re: My Optics Education Project (MOEP)

[dykstrad@varney.idbsu.edu (Dewey Dykstra, Jr.)]

> On Thu, 30 May 1996 nafindley@vassar.edu wrote:
>
> > Hello All,
> >         My name is Nate Findley, I am a research fellow at Vassar College
> > and I am working under Cindy Schwarz.  One of our projects this summer is
> > to create a diagnostic exam that professors can use to test student's
> > qualitative knowledge of optics.  We are trying to figure out what concepts
> > students have trouble with in optics so, similarly to the FCI, the test
> > will show the difference before and after a intro physics course.  If
> > anyone can help us with our problem that would be great!  Also, any
> > comments and questions are welcome.
>
> Hi Nate!
>
> There was some work in just this subject done by Goldberg &McDermott,
> paper in AJP called something like "Student misconceptions about images
> formed by converging lenses and concave mirrors."  Students drew a
> particular incorrect diagram when asked to explain how a lens formed an
> image. After an intro optics course some of them drew an accurate diagram
> and some still drew the incorrect one, indicating that their misconception
> was tenacious, and was not dislodged by the course work.
>
> There's a bit about this on my Misconceptions page,
>   http://www.eskimo.com/~billb/miscon/lens.html
>
> I think there is a reference for the McDermott paper towards the end.
>
> My "lens.html" article is an attempt to point out that some optics
> misconceptions do not arise spontaneously in students, they are
> specifically taught in earlier grades!  The misconceptions are almost
> impossible to dislodge from the textbooks, since numerous books contain
> the same error and this constitutes a mistaken "concensual reality" on the
> part of the authors which strongly resists change.


Several points are important here:
1.  It is virtually impossible to write a diagnostic of student alternative
conceptions when one _starts_ with an outline of the scientists' view,
especially one which ranges over at least two models of light.
2.  There is a distinction between alternative conceptions and
misconceptions, which is unfortunately not recognized by many.  Some of the
notions students have about light come from spontaneous thinking about
experiences with light, others come specifically from teaching which
intends to transmit knowledge instead of allowing students to construct it.
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?)
3.  If all one is interested in is whether the students can answer as the
scientists do, why not just write a conceptual final exam and be done with
it?

Dewey

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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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