Probing student understanding of total internal reflection and optical fibers using Piaget-style interviews conducted both face-to-face and electronically DJ Wagner 1,2, JJ Rivera 1, Fran Mateycik 1, and Sybillyn Jennings 3 1 Rensselaer Polytechnic Institute, 2 Grove City College, 3 Russell Sage College The Context: The Science of Information Technology (ScIT) introduces students of all majors to the physical principles behind the operation of information systems. NSF is supporting current efforts to make ScIT materials useful to a large audience. As part of that effort, we are designing diagnostic questions addressing the topics covered in ScIT. Diagnostic questions are most useful when they address student preconceptions and distinguish between different cognitive models [1]. Clinical Interviews have long been regarded as an effective means of eliciting students’ conceptual frameworks [1-3]. Piaget [3] developed the method of critical exploration to see what thoughts lay behind a child’s initial answer to a question, and the PER community has used this method extensively [1-2]. We used Piaget-style interviews to study students’ understanding of total internal reflection (TIR) and how TIR relates to the operation of optical fibers. The Study: “What is an optical fiber and what does it do?” Follow-up questions included “How does the fiber keep the light from escaping?” and “What can you tell me about refraction?” RPI work supported in part by NSF CCLI Program under grant DUE Thanks as well to Leo Schowalter for access to ScIT students, and to the rest of the ScIT advisory committee: Karen Cummings, Toh-Ming Lu, Saroj Nayak, Jim Napolitano, Peter Persans, and Wayne Roberge. Conclusions about Mental Models: We identified the following 7 stages of cognitive understanding, based on the interview responses. Most stages were seen in e-interviews as well as face-to-face interviews. No concept of light carrying signal Light just needs to be contained (by, e.g., dark coating) Fibers use mirrored surface or other non- refractive reflection Use phrase “Total Internal Reflection” Recognize that fibers work through refractive effect Can explain TIR in terms of Snell’s Law Can explain TIR “to someone who doesn’t know what a sine function is.” Novice Expert Comparing E-Interviews with Traditional Face-to-Face Interviews Advantages of E-InterviewsDisadvantages of E-Interviews  Minimal transcription needed!!! (WebCT records conversations in Chat Rooms 1-4.)  Can be conducted from wherever, whenever, and however is convenient (at home, listening to music, eating ice cream, in jammies, etc.).  Can hold 2 or 3 interviews simultaneously, typing questions for student 3 while students 1 and 2 are typing their responses. (4 at a time is a bit much.)  Typed thoughts often come across more coherently than spoken thoughts.  Apparent anonymity lets students express their lack of knowledge with less embarrassment.  Slowness of typing (vs. speech) results in longer time to gain comparable amount of data: the median time for an e-interview was 5 times the median for face-to-face interviews.  Less personal connection between interviewer and interviewee: can’t read body language; must establish rapport over distance.  Students might be multitasking too – not quite a controlled environment.  Student cannot draw; difficult for instructor to provide images.  Some students may be uncomfortable using Chat Room to communicate. Conclusions about Interview Formats: E-interviews can provide valuable information about cognitive models. They provide some advantages over face-to-face interviews but have their own set of limitations. Instructor time is smaller in e-interviews, due to decrease in transcription time; student time is greater in e-interviews. Several students called the e-interview “fun” or “interesting” Demographics of Interviewees 5 In-Service Teachers 2 Physics Faculty 22 ScIT Pre- Instruction 5 Physics Students (REU) 8 ScIT Post- Instruction Information StorageInformation ProcessingFuture IT ScIT Content Grey = Not Available Red = Original Format Yellow = Revision Begun Green = Revision Complete Blue = Internally Reviewed Purple = Externally Reviewed Organization and Status of Materials: Materials located at Faculty, REU students, and in- service (non-physics) teachers were interviewed in a traditional (face-to-face) form in the Summer of ScIT students (both pre- and post-instruction) were interviewed via WebCT’s Chat Room in the Spring of Photograph of Optical Fiber next to sewing needle. The core of the fiber is 62 microns in diameter; the cladding is 125 microns. Laser light trapped in a plastic fiber. Air serves as the cladding. [1] Lillian C. McDermott, “Bridging the Gap Between Teaching and Learning: The Role of Research,” The Changing Role of Physics Departments in Modern Universities: Proceedings of ICUPE, ed. by E. F. Redish and J.S. Rigden. [2] E. Hunt and J. Minstrell, “A Cognitive Approach to the Teaching of Physics,” Classroom Lessons: Integrating Cognitive Theory and Classroom Practice, ed. by McGilly (MIT Press, 1994). [3] J. Piaget, The child’s conception of the world, trans. by J. & A. Tomlinson. (Littlefield, NJ, 1926/1972).