Using Students' Preconceptions to Improve Upon

1
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. Problems Many of
the original questions were fact-based rather
than conceptual. After the first trial, using
PER literature as 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.

• EXAMPLE
• The critical angle of an interface between two
  materials is
• The angle of incidence at which light reflected
  from the denser material is polarized.
• the anglee of incidence at which light reflected
  from rarer material is polarized
• The angle of incidence at which light entering
  the denser material is completely reflected.
• The angle of incidence at which light entering th
  rarer material is completely reflected.
• All of the above.

• 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
• Limits of the Open-Ended Responses
• 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
  students 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
• 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

What does the fiber look like? (How is it made?)
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 open- ended 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 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 werent
there, the light would escape when it struck the
side of the fiber. Student B I dont 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 wont let the light out. The
light cant 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.
Selected Pre-Instruction Answers 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 dont 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
wont just bend wihtout changing mediums so that
doesnt 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.
General Conclusions 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.
3 Rules of the Trade Rule 1 Dont
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.

• Science of Information Technology Reflection,
  Refraction, and Optical Fibers Module,
  http//www.rpi.edu/dept/phys/ScIT/InformationTrans
  fer/reflrefr/rr_index.htm
• 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).
• Jim Minstrell, Helping Teachers Attend to
  Student Thinking, For Teacher Education
  Materials Project, www.te-mat.org/minstrell_pf.sht
  ml.

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/p
apers/pdf/plenary.pdf
This work supported in part by NSF CCLI Program
under grant DUE-0089399. Thanks to DJ Wagner,
Sybillyn Jennings, and JJ Rivera