Using Students' Preconceptions to Improve Upon
Curricular Materials
Frances Mateycik, Rensselaer Polytechnic Institute, Troy, NY 12180
Advisor: DJ Wagner
Abstract:
The Science of Information Technology (ScIT) is a course at Rensselaer introducing students to the physics underlying IT. We are currently expanding the online curriculum to facilitate
widespread use beyond the Rensselaer course. As part of the development of the prototype module, 1 we are assessing students' understanding of total internal reflection (TIR) and optical
fibers through the use of clinical interviews. Findings drawn from these interviews are used both to check whether the revised materials address students' preconceptions and to develop a
multiple-choice diagnostic tool. We have piloted the diagnostic questions on TIR and optical fibers with three different groups of physics students. We will present aspects of the conceptual
and methodological findings and discuss how we are using these findings to refine both the curricular materials and the diagnostic questions.
Part of our ongoing development process is to asses student preconceptions associated with different levels of comprehension. The Physics Education Research (PER) literature abounds with
studies of preconceptions,2 but few studies have examined how students approached the topics that form the backbone of ScIT: e.g., total internal relfection (TIR), and semiconductor physics.
Like many before us, 3,4 we used clinical interviews to open a window into student understanding of our target topics - optical fibers, refraction, and TIR.
Goal: Create a diagnostic tool similar to the FCI made up of carefully constructed multiple choice questions
that amplify the significance of student responses and give an opportunity for students to use their
preconceptions.3
First Step: The original MC diagnostic was put together during the first offering of the ScIT course at RPI. We wanted to know
both the initial state of students and whether students learned anything after the course was over.
EXAMPLE:
The critical angle of an interface between two materials is:
a) The angle of incidence at which light reflected from the denser material is polarized.
b) the anglee of incidence at which light reflected from rarer material is polarized
c) The angle of incidence at which light entering the denser material is completely reflected.
d) The angle of incidence at which light entering th rarer material is completely reflected.
Problems: Many of the original questions were fact-based rather than conceptual. After the first trial, using PER literature as
e) All of the above.
a stepping stone, and data from the original diagnostic, questions were added on material not initially covered, and others were
re-worded to better probe student preconceptions.
Second Step: Open-ended questions were created to supplement data coming from the diagnostic and refine future
versions of the MC diagnostic.
Need for some Open-Ended Responses:
•“Short responses (even if correct) do not necessarily indicate understanding. Probing in depth is necessary for making a
correct assessment of student learning.”4
•“the diverse data obtained by the open-ended questions, though more dependent on interpretation, are indispensable if one
aims at revealing facets of knowledge.”2
Original MC
Diagnostic
Open-Ended
Questions
Limits of the Open-Ended Responses:
Interviews
Conducted
Student
Feedback
Future
Revisions
Revision of MC
Diagnostic
Open-Ended Answer yields temptation to read meanings into student answers:
A student responds that “the reflectivity of the fiber” is what keeps light from escaping a fiber. It is tempting to conclude
that this student has a misconception of fibers having a mirrored coating, but no way to tell for sure from this student’s
response
•Open-Ended Answer yields only partial glimpse of student understanding.
EXAMPLE:
Question Asked: “How does an optical fiber work?”
Selected answers:
1. “When it bends it is reflected back to the other side of the
fiber and not out.”
2. “The sheilding of a Fiber”
3. “Whether or not the optical fibers is plugged into a black
hole somewhere an outer space.”
Interviews and Results:
Third Step: As an answer to some of our limitations using both MC diagnostic results and open ended responses, face to face and electronic interviews were conducted as a way to refine our
current diagnostic tools, gauge how different curricula affect students’ understanding of refraction, TIR, and Optical Fibers, and to confirm our expected results while finding the unexpected.
Can you tell me what an optical fiber is (what does it do?)?
Though interviews are most helpful it must be noted that they are not practical for larger groups
and statistics since they take time and one needs to put out a lot of effort.
It transfers information by passing pulses of light through
the fibers of the wire.
Expected and Unexpected misconceptions arose, like:
What does the fiber look like? (How is it made?)
•The existence of mirror-coating in an optical fiber was a common misconception confirmed
•Physics majors (and physicists) would have difficulty explaining concepts such as TIR without
equations
•The term “fiber optics” may resonate with more people than “optical fibers”
•The misconception that angle of refraction exceeds 90 degrees when TIR occurs
•Prior experiences (childhood toys and memories) have very large effect on students’
conceptions
I don't know how they make it, but it is made of glass.
What prevents the light from escaping and keeps it traveling down the wire?
I am not sure, possibly an electric current….The current would be in a parallel wire,
changing the conductivity of the glass causing the light to travel down the fiber.
Do you think any of the light escapes?
A type of rubber, it keeps the light in the fiber.
From this transcript of an actual (pre-instruction) interview, we
can see that there are just certain ideas which students come up
with in an interview that would never have been elicited using
instructor-thought-up multiple-choice questions.
Fourth Step: This last semesters’ revised MC/Open-Ended DiagnosticWhile current revisions
of the MC Diagnostic examination were improved upon using the openended questions and the interviews, it can be seen from the results on the table to the right
that not all of the questions yield positive Gain.
EXAMPLE:
Selected Pre-Instruction Answers:
Three students of an introductory physics course such as yours are discussing the operation of optical fibers. Their comments are shown
below. Which student(s) do you agree with, and why? (Agreeing with non of the students is an option.) Please justify your answer with an
explanation that the three students would understand.
Student A: “Optical fibers re an amazing work of engineering. Imagine being able to place a tiny mirror inside the fiber at each place the fiber
bends! If those mirros weren’t there, the light would escape when it struck the side of the fiber.”
Student B: “I don’t think you need mirrors placed inside the fibers at particular locations. The fiber should be able to bend at any point, right?
I think there is some other physics principle involved. Maybe something happens to the light when it tries to leave the fiber.”
Student C: “Something happens, all right. The light hits the dark coating of the fiber, which won’t let the light out. The light can’t get past that
dark coating, so it is trapped and travels to the end of the fiber.”
Student A: “I still think mirrors are involved, but I agree that placing mirrors where the fiber will bend is a bit awkward. Perhaps the entire
inner surface of the fiber, except the ends where the light enters and exits, is coated with a silvery substance that acts like a mirror.”
General Conclusions:
Answer 1: “ I agree with Student A. I think that the entire fiber is coated with a reflective matierial because relfection is
the only way to redirect light without losing any energy. It is like an elastic collision. There is no law that causes light to
bend and of itself as B stated with the exception perhaps of gravity in the case of extrememly large bodies such as a star
or galaxy when light behaves as a particle. In response to C, the absorbtion of the light by rubber would be counter
productive because the “signal” would thus be absorbed and never reach the receiver”
Answer 2: “I do not agree with any of the students. I will be honest and say I know nothing about optical fiers but none of
the arguments make sense to me. The first comment by student A sounds plausible but I don’t think mirrors reflect 100%
so a fair amound of the light would be lost. Same thing for the second comment made by student A. Student B said that
the light should bend with the fiber but light won’t just bend wihtout changing mediums so that doesn’t make sense to me
either. Student C said the light would be trapped by dark walls but I believe a lot of light would be lost. Dark walls would
not reflect the light. So, in conclusion, I do not agree with any of the students.
3 Rules of the Trade:
Interviews, previous MC diagnostic examination results, and data from the previous open ended
questions have influenced the development of ScIT material in many instances. Dispersion
through a prism is no longer in the refraction module but in a module discussing signal loss and
distortion. Diagnostic questions involving optical fibers now begin with the explanation that fibers
carry information in the form of light pulses. A photograph may be added to the diagnostic of a
toy using fibers to explicitly connect to students’ prior experiences, T/F will become “which most
important..” MC questions, and the MC question relating students’ past quotations to their own
perception will include a fourth category of “none of the above.”
Rule 1: Don’t reinvent the wheel
Lots of research done about student (mis)conceptions of commonly-covered introductory
physics topics. Redish and McDermott produced resource paper in AJP with lots of good
references.3
Rule 2: Use results of research judiciously.
Talk to your students, and see how their ideas compare to those presented in literature.
Rule 3: There is no substitute for (recorded) interviews, giving the student an opportunity to
clarify and think about his or her responses.
1. Science of Information Technology Reflection, Refraction, and Optical Fibers Module, http://www.rpi.edu/dept/phys/ScIT/InformationTransfer/reflrefr/rr_index.htm
2. Igal Galili and Amnon Hazan, “The influence of an historically oriented course on students' content knowledge in optics evaluated by means of facets-schemes analysis,” "Phys. Educ. Res., Am. J. Phys 68 (S1) S3 (2000).
3. Jim Minstrell, “Helping Teachers Attend to Student Thinking,” For Teacher Education Materials Project, www.te-mat.org/minstrell_pf.shtml.
This work supported in part by NSF CCLI Program under grant DUE-0089399.
Thanks to DJ Wagner, Sybillyn Jennings, and JJ Rivera
4. Lillian C. McDermott, “Bridging the Gap Between Teaching and Learning: The Role of Research,” CP399, The Changing Role of Physics Departments in Modern
Universities: Proceedings of ICUPE, edited by E.F. Redish and J.S.Rigden, 1997 AIP. http://www.psrc-online.org/classrooms/papers/pdf/plenary.pdf