This article illustrates the use of research as a basis for the development of curriculum on physical optics. Evidence is presented that university students who have studied physics at the introductory level and beyond often do not have a functional understanding of the wave model for light. Identification and analysis of student difficulties guided the design of a set of tutorials to supplement instruction in a standard calculus-based or algebra-based course. Ongoing assessment was an integral part of the curriculum development process. The instructional materials that resulted have proved to be effective at helping students construct and apply a basic wave model for light.
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The term functional understanding is used to connote the ability of students to apply concepts and reasoning in situations other than those explicitly studied. The degree of transfer to be expected depends on the population and the difficulty of the concepts.
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Pretests and post-tests are never identical. In some cases, the post-tests are similar to the pretests and permit us to assess how well students are able to apply a concept in the context in which it was learned. In other cases, the post-tests require a greater degree of transfer. In any case, the questions are such that students are not able to respond on the basis of a memorized answer. Post-test questions are given on midterm or final examinations. In general, we have found that results do not depend on whether a post-test is given within 2–3 weeks of the tutorial or at the end of the quarter.
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13.
In the development of the tutorials we have drawn upon our experience with other research-based instructional materials. See, for example, L. C. McDermott and the Physics Education Group at the University of Washington, Physics by Inquiry (Wiley, New York, 1996), Vols. I and II.
16.
Additional evidence that student performance on certain types of questions is essentially the same before and after standard instruction can be found in Refs. 1, 2, 6, and 9. Other examples can be found in
R. R.
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In some textbook treatments of physical optics, a converging lens is placed between the slits and the screen. We have found that students have difficulty with such diagrams. Because of the limited time available, we have restricted the treatment in the tutorials to the approximation of a very distant screen.
18.
In this article, a very narrow slit is one for which the intensity is essentially uniform on a semicircular screen centered on the slit. The width must be much less than the wavelength of the incident light for this approximation to hold. If only the central portion of a flat screen is considered, this condition may be relaxed somewhat. Also, since a slit has finite height, a very narrow slit does not act as a point source but can be modeled as a vertical line of point sources. This complication is not discussed in the tutorial.
19.
For example, one instructor devoted considerable time to illustrating the use of phasors to solve a variety of problems in interference and diffraction. On a final examination, he asked students to draw phasor diagrams for various screen locations for three sources of coherent waves a distance d from one another. Very few of the students drew correct diagrams. Approximately one-third drew diagrams in which the angle between consecutive phasors was the spatial angle θ rather than
20.
Typically, we have found that students take the pretests seriously. Performance on specific questions has been essentially the same whether given as an ungraded pretest or on a course examination.
21.
See, for example,
B.
Thacker
, E.
Kim
, K.
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, and S. M.
Lea
, “Comparing problem-solving performance of physics students in inquiry-based and traditional introductory courses
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(1994
);E. Mazur, Peer Instruction, A User’s Manual (Prentice Hall, Upper Saddle River, NJ, 1997). Similar results have been reported at AAPT meetings by R. Chabay and B. Sherwood.
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© 1999 American Association of Physics Teachers.
1999
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