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Light emitting diodes have been used to determine Planck's constant in introductory physics laboratories. One common method relies on the energy of the light emitted by the LED and its relation to the energy gap in the solid of which the diode is composed. However, there could be a problem with the data that are collected for this experiment. For some LEDs the energy of the light emitted from the LED can be quite different from the gap energy. If these LEDs are used for the experiment, the results will give different results for Planck's constant.

Pencasts are videos of problem solving with narration by the problem solver. Pedagogically, students can create pencasts to illustrate their own problem solving to the instructor or to their peers. Pencasts have implications for teaching at multiple levels from elementary grades through university courses. In this article, we describe the use of pencasts in a university-level upper-division electromagnetic fields course usually taken by junior and senior physics majors. For each homework assignment, students created and submitted pencasts of ordinary problems several days before the problem set was due. We compare students' performance in the class (grades for pencast submission excluded) with the pencast submission rate. Students who submitted more pencasts tend to do better in the course. We conclude with some practical suggestions for implementing pencasts in other courses.

Computer-automated assessment of students' text responses to short-answer questions represents an important enabling technology for online learning environments. We have investigated the use of machine learning to train computer models capable of automatically classifying short-answer responses and assessed the results. Our investigations are part of a project to develop and test an interactive learning environment designed to help students learn introductory physics concepts. The system is designed around an interactive video tutoring interface. We have analyzed 9 with about 150 responses or less. We observe for 4 of the 9 automated assessment with interrater agreement of 70% or better with the human rater. This level of agreement may represent a baseline for practical utility in instruction and indicates that the method warrants further investigation for use in this type of application. Our results also suggest strategies that may be useful for writing activities and questions that are more appropriate for automated assessment. These strategies include building activities that have relatively few conceptually distinct ways of perceiving the physical behavior of relatively few physical objects. Further success in this direction may allow us to promote interactivity and better provide feedback in online learning systems. These capabilities could enable our system to function more like a real tutor.

We investigated introductory physics students' mental models of sound propagation. We used a phenomenographic method to analyze the data in the study. In addition to the scientifically accepted Wave model, students used the "Entity" model to describe the propagation of sound. In this latter model sound is a self-standing entity, different from the medium through which it propagates. All other observed alternative models contain elements of both Entity and Wave models, but at the same time are distinct from each of the constituent models. We called these models "hybrid" or "blend" models. We discuss how students use these models in various contexts before and after instruction and how our findings contribute to the understanding of conceptual change. Implications of our findings for teaching are summarized. (Contains 14 figures.)

In prior research, the classification of concepts into three types--descriptive, hypothetical and theoretical--has allowed for the association of students' use of different concept types with their level of understanding. Previous studies have also examined the ways in which students link concepts to determine whether students have a meaningful understanding of principles of evolution. In this study, we build on our previous work that seeks to examine how students use prior knowledge in new situations and context, as well as present an adaptation of concept and concept-link categorization previously used in biology education research. In this adaptation, concepts are categorized on the basis of the observability of the concept exemplars and are shown to be dependent upon the knowledge level of the student. We use this categorization method to examine how students use prior knowledge when presented with an opportunity to apply physics in a new context, namely, wavefront aberrometry. Results indicate that students primarily utilize lower-level concepts, which is in agreement with previous research findings. We also found that students are able to create links between different levels of concepts, and that the type of links created can give insight to how deeply they understood the physics of the new context. (Contains 1 table and 5 figures.) [A 28-item list of references and notes is provided.]

A whiplash event is a relative motion between the head and torso that occurs in rear-end automobile collisions. In particular, the large inertia of the head results in a horizontal translation relative to the thorax. This paper describes a simulation of the motion of the head and neck during a rear-end (whiplash) collision. A head-neck model that qualitatively undergoes the same forces acting in whiplash and shows the same behavior is used to analyze the kinematics of both the head and the cervical spine and the resulting neck loads. The rapid acceleration during a whiplash event causes the extension and flexion of the cervical spine, which in turn can cause dislocated vertebrae, torn ligaments, intervertebral disc herniation, and other trauma that appear to be the likely causes of subsequent painful headache or neck pain symptoms. Thus, whiplash provides a connection between the dynamics of the human body and physics. Its treatment can enliven the usual teaching in kinematics, and both theoretical and experimental approaches provide an interesting biological context to teach introductory principles of mechanics.

In spite of advances in physics pedagogy, the lecture is by far the most widely used format of instruction. We investigated students' understanding and perceptions of the content delivered during a physics lecture. A group of experts (physics instructors) also participated in the study as a reference for the comparison. During the study, all participants responded to a written conceptual survey on sound propagation. Next, they looked for answers to the survey questions in a videotaped lecture by a nationally known teacher. As they viewed the lecture, they indicated instances, if any, in which the survey questions were answered during the lecture. They also wrote down (and if needed, later explained) the answer, which they perceived was given by the instructor in the video lecture. Students who participated in the study were enrolled in a conceptual physics course and had already covered the topic in class before the study. We discuss and compare students' and experts' responses to the survey questions before and after the lecture.

Photorefraction is a method to easily estimate the refractive state of the eye. The principle of photorefraction involves projecting light into the eye during flash photography and then examining the paths of light that emerge from the pupil after scattering on the back portion of the interior of the eyeball (fundus). We will explain the optical principles underlying the method for eccentric photorefraction and describe how students can perform it using current digital cameras. Our purpose is not to diagnose refractive errors reliably, but to use devices popular among young people that, in combination with an important ophthalmic context, may be successful in improving students' interest for learning optical concepts.

Studies the role of context in students' uses of alternative conceptual models by using Newton's third law. Identifies four contextual features that are frequently used by students in their reasoning. Probes the effects of specific contextual features on student reasoning using a multiple-choice survey. (Contains 39 references.) (Author/YDS)

Explains a hands-on approach to teaching quantum mechanics that challenges the belief shared by many physics instructors that quantum mechanics is a very abstract subject that cannot be understood until students have learned much of the classical physics. (Contains 23 references.) (Author/YDS)

Discussion of multilingual teaching environments focuses on the development of instructional software that is able to change the language of the on-screen presentation. Benefits for second-language learning are discussed, programing methods are explained, and an example of a software program in English and in German is given. (LRW)

Discusses the design of introductory physics course for elementary education majors and nonscience majors. Describes the learning cycle used for constructing hands-on activities. Provides an example of a week's activity on energy. Presents an evaluation of the course based on examinations and the teacher's impressions. (YP)

We have compared students' responses on four multiple-choice force concept inventory (FCI) questions with similar responses to equivalent open-ended questions. Our results indicate a good agreement between the percentages of correct responses in each of the two formats, indicating that distracters on the FCI do not adversely affect performance as measured by the number of correct answers. However, a significant percentage of the open-ended responses fall into categories that are not included in the FCI multiple choices. When these alternative categories were presented to the students as distracters in a revised multiple-choice format, a significant percentage of the students chose these alternative responses.

The concept of potential-energy diagrams is of fundamental importance in the study of quantum physics. Yet, students are rarely exposed to this powerful alternative description in introductory classes and thus have difficulty comprehending its significance when they encounter it in beginning-level quantum courses. We describe a learning unit that incorporates a sequence of computer-interfaced experiments using dynamics or air-track systems. This unit is designed to make the learning of potential-energy diagrams less abstract. Students begin by constructing the harmonic or square-well potential diagrams using either the velocity data and assuming conservation of energy or the force-displacement graph for the elastic interaction of an object constrained by springs or bouncing off springy blocks. Then, they investigate the motion of a rider magnet interacting with a configuration of field magnets and plot directly the potential-energy diagrams using a magnetic field sensor. The ease of measurement allows exploring the motion in a large variety of potential shapes in a short duration class.

We present here a computer program - the Semiconductor Device Simulator - which simulates the working of three p-n junction devices: the light-emitting diode, the solar cell, and the tunnel diode. This program enables students to create the device starting with two pieces of intrinsic semiconductor material, and doping them appropriately to create a p-n junction device of their choice. While creating the device, students can observe the changes in the energy bands and Fermi level as a response to doping. The device, once created, can then be incorporated into a circuit where the students can observe the energy bands, the I-V graph, as well as the intensity spectrum of the device in response to the changes in applied voltage and/or incident light. No prior knowledge of higher level mathematics is required to use the program. The program is available for Windows[TM] and Macintosh[TM] platforms. The flexibility of the program allows it to be used by students over a range of academic levels. We have field tested the program along with associated materials in both high school and university environments. The current version of the program contains modifications based on these field tests.

Teaching physics by lectures does not provide a very effective learning environment and can be replaced by learning cycles. Learning cycles are usually effective for a class of at most 30 students but they can also be used for much larger classes. The cycle consists of exploration experiments, discussions, teaching of new concepts, and applications. The cycle can be augmented by using digital video and computers to help students visualize abstract concepts.

Interactive video is an effective medium for teaching physics. The technology allows teachers to control the audiovisual session or pass control to students. Interactive video relates physics with real-life situations and has been proven to be an efficient laboratory tool.

An interactive, instructional videodisc was produced using films on wave motion/vibrations and Tacoma Narrows bridge collapse. The disc is appropriate for three levels of physics (physics/algebra; physics/calculus; non-major physics). Program sections (introduction to videodisc player, bridge collapse, influence of wind, bridge properties, and conclusion) are discussed. (JN)