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Mark F. Masters
Much of my research (atomic and molecular spectroscopy) involves the use of simple geometric optics to set up light collection systems. Unfortunately, students involved in my research often have had to be re-taught basic optics. For example, students would assemble frustratingly poor optical systems based on stacked books and even, on one occasion, a Coke™ bottle. These students had, at a minimum, an exposure to optics in their introductory classes, but a disturbingly large fraction had actually completed an intermediate optics class and its associated laboratory. Clearly, the students had not fully integrated their understanding of optics.
Optics is a very important aspect of the physics curriculum. Typical topics include basic geometric optics and physical optics. If one considers the traditional introductory physics class as part of a two semester sequence, all topics within optics might be covered in approximately four or five weeks. The traditional introductory laboratory might allow for five demonstrations or as in our case of single topic laboratories (DC circuits), not covered at all. This is simply not enough time for students to achieve any understanding of this topic. The intermediate optics class is typically built upon this weak foundation. It rapidly reviews the optics that the students should have mastered in the introductory class and then gives the students a highly mathematical representation of the physics. The laboratory is often a sequence of guided demonstrations. Unfortunately, our evidence indicated that the students were not learning what was intended. To correct this situation we started a complete revision of our optics course and associated laboratory to assist the students in constructing an "optics framework".
We started the revisions with consideration that the students were almost always engaged in "answer-making" rather than "sense-making." "Answer-making" is the ability to come up with some form of an answer without the ability to explain how that answer is reasonable and how that answer makes sense. It typically involves "plug-n-chug" types of problems. "Sense-making" is coming up with the explanations and requires understanding of the subject at hand. "Sense-making" requires a deeper understanding of the material.
With the goal of producing "sense-makers", the lecture component of our optics class was changed so that it employed interactive engagement and used tutorials to build understanding and mathematical sophistication for the students. However, providing hands-on activities in the laboratory in such a way that the students were not simply following directions but discovering the optics was deemed critical. As such, we expended significant effort in revising these laboratories such that the students would discover the physics rather than simply be told. The laboratories were designed so that later laboratories built upon the earlier experiences so that students could not follow a "memorize and dump" procedure.
Unfortunately, this laboratory format significantly curtails the number of topics that can be explored through laboratory. For this reason our laboratories concentrate on geometrical optics and polarization with the bulk of the laboratories on geometrical optics. Physical optics was not included because we found that meaningful investigations would exceed the time we had available and simpler physical optics investigations devolved into instruction based rather than discovery. The laboratories are described in Ref  and are available on the web .
As with any investigation, it is important to assess the results to determine whether the "experiment" is successful. For this project, we examined two cohorts of students and we use two methods to collect and evaluate the data. The first data is from embedded questions within the laboratories. We look at the student ability to answer the questions ("answer-making") and their ability explain their answers ("sense-making"). This method was used for both cohorts. The second set of data was used only for the second cohort. It involved administering a preliminary version of an optics concept assessment that we have been developing  as a pre- post-test and examining student improvement.
Using the pre- post-test for the second cohort, we found that students who took the optics laboratory (physics majors) demonstrated significantly greater improvement than those who did not (engineering majors). This indicates that the laboratory makes a difference in student learning of optics.
Using the embedded questions we found that as the semester progressed the students in the first cohort demonstrated a marked improvement in the quality of their explanations. The students in this cohort started an emphasis on answer-making with poor or novice explanations, but by the end of the semester, the explanations were approaching what we classified as professional. For the second cohort we also found improvement in the progress from answer making to sense-making. However, it was not as significant as for the first cohort. So why was that?
For years we have been asking the students about their introductory laboratory experience when they come to our modern physics laboratory. We ask this question because we do not have department-wide laboratories. Some of the laboratories are discovery based and engage the students while others are much more cookbook. When we compare the introductory laboratory experiences of the first cohort with the second, we find that the first cohort was provided with the former while the latter were given largely cookbook type experiences. The introductory laboratory sets the "stage" for student expectations in later advanced laboratories. These expectations are very difficult or even impossible to change in later lab experiences.
We have also observed that class format has a significant impact on how the students approach laboratory and student performance in the laboratory. Given open-ended, discovery based laboratories, students in a traditional lecture class will struggle much more significantly than the students with an active learning class. The skill of inquiry must be developed and nurtured in both class and laboratory.
What are labs for and preparing students for research
These laboratories have alleviated some of the problems of bringing students into the research laboratory. When they enter (after taking the optics class), we do not need to teach them basic optics to get them started. At the same time, there is the lack of exposure of the students to physical optics. This problem is alleviated by a class (and laboratory) on physical optics and interferometry.
The larger question is: what are we (as physicists) trying to achieve through laboratory. The data we have examined indicate that laboratory and class are coupled; that the introductory laboratory format is of critical importance to later laboratory experiences; and that laboratory can have a significant impact on student learning. I believe that laboratories must emphasize inquiry and discovery. We cannot provide the students with simple follow-the-directions experiences and then expect the students to suddenly become, and have the skills to be, inquisitive. Laboratories must model what we expect of the students.
 Mark F. Masters and Timothy T. Grove, "Active learning in intermediate optics through concept building laboratories," Am. J. Phys., 78, 485 (2010).
 Laboratories and tutorials are available at http://users.ipfw.edu/masters/Optics%20CCLI%20Project/optics_ccli_project.htm
 For information about the Optics Concept Assessment please contact Timothy T. Grove.
Mark F. Masters is a Professor of Physics at Indiana University-Purdue University Fort Wayne.