STUDENT DESCRIPTIONS OF REFRACTION AND OPTICAL FIBERS
INTRODUCTION
Since 1999, Rensselaer has offered The Science of Information Technology (ScIT) to a total of 158
academically diverse students [1]. This innovative course teaches the scientific principles behind the
operation of computing systems. For example, in ScIT we apply the phenomenon of total internal reflection
(TIR) – a topic commonly covered in more traditional physics courses – to optical fibers, a technology
eminently relevant to the students. Our current project aims to modify and expand ScIT curricular
materials [2] for widespread dissemination over the Internet, with the goal of fostering instruction that
connects physics with contexts that interest today’s students.
Part of our ongoing development process is to assess student preconceptions associated with different
levels of comprehension. The Physics Education Research (PER) literature abounds with studies of
preconceptions [3], but few studies have examined how students approach the topics that form the
backbone of ScIT: e.g., total internal reflection (TIR), propagation of signals, semiconductor physics, or
quantum effects on microelectronics. (An exception is a recent study [4] on student understanding of
quantum physics and conductivity.) We chose to conduct a study of student thoughts on total internal
reflection and optical fibers.
We initially conducted face-to-face interviews with a sample of 12 volunteers with diverse physics
experience. When such face-to-face interviews with ScIT students were not possible, we conducted “einterviews.[20]” In this paper we present our categorizations of student responses, discuss how we are
modifying our materials to address these findings, and impart methods used to refine our multiple choice
diagnostic questions for future curricular development.
[20] (In a separate paper, we discuss our experience with both interview formats.)
METHODOLOGY
Clinical interviews have been widely accepted as an effective means of eliciting learners’ reasoning and
conceptual frameworks. The PER community has its own strong history of using such interviews to
effectively probe student comprehension about a physics-related concept. With video recordings and
written transcripts in hand, the interviews were filtered through several times looking for patterns and
progressions between all 32 students of various physics backgrounds and 2 professors at RPI.
As similar preconceptions correlating to statements in the transcripts began to repeat among the
interviewees, network schematics were drafted, and patterns emerged. The schematics were roughly
outlined at first, and then remodeled to include all interviewee preconceptions. Through this process, it
resulted that optical fibers and refraction could not be grouped together since there were limitations on how
much data we could draw from the refraction discussions. Time limitations and the direction taken during
the interview determined how deeply we were able to probe the subjects and as a result, we were been able
to construct a network model of student understanding of optical fibers, but not for refraction. We did find
the data useful in that a preliminary tree was developed in an effort to understand the many paths taken by
the interviewees.
Also, while taking in data for the interviews, we found many of the preconceptions found correlated
with the answers given by students that had taken pre- and post- multiple choice diagnostic examinations
including questions related to optical fibers, refraction, and TIR. These preconceptions could be used to
understand why some questions scored higher gains than others, and we found could help explain negative
gain which occurred within the results of the diagnostic.