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Seeing into the Quantum World

James Brown

Pages: pp. 44-45

M. Belloni, W. Christian, and A. Cox, Physlet Quantum Physics: An Interactive Introduction, Prentice Hall, 2005, ISBN: 0131019708, 224 pages.

One of my colleagues recently reminded me of the difficulty of "Teaching Newtonian Mechanics to Aristotelian Minds in a Quantum World," a problem that most of us recognize. At least part of this problem arises from a disconnection between students' visions of the world and the mathematical models provided in the classroom. The physlet approach helps bridge this gap by providing tools that not only allow students to visualize quantum mechanical phenomena, but also allow them to develop a set of experiences from which they can begin to develop a "new intuition" into what for most of us is a nonintuitive subject. This is where the authors of Physlet Quantum Physics: An Interactive Introduction have succeeded to a great extent.

Depth of Field

The book and accompanying CD-ROM contain a series of roughly 250 Java applets covering topics appropriate to several courses, including special relativity, experiments from the turn of the 20th century that motivated the development of quantum theory, and introductory quantum mechanics, as well as applied topics in statistical mechanics, solid-state, and nuclear physics. The material on special relativity spans from the relativity of simultaneity through basic relativistic mechanics. The authors offer the motivation for quantum theory through a series of applets on black-body radiation, Brownian motion, Rutherford scattering, and the Bohr atom, among others. They also discuss wave particle duality in the context of the double slit experiment and the photoelectric effect. The material on quantum theory represents eight of the 15 chapters in the book; the book concludes with two chapters on applied topics.

Much of the material would be appropriate to that oft-misnamed sophomore course "Modern Physics," whereas other parts would find good homes in a junior- or senior-level course on quantum mechanics or the appropriate topical course. In each chapter, the authors guide the reader through several simulations that illustrate the pertinent physics, followed by several exercises. In the simulation and exercises, students either vary parameters in the simulation or make virtual measurements from it. In these ways, the simulations serve not only as a visualization tool to test students' solutions, but also as a "virtual laboratory" for making and testing their own predictions. The book doesn't attempt to be the primary text for any course, but it could serve as a resource for faculty wanting to incorporate more modern instructional methods into their teaching of these topics. Other works have tried to do similar things, including Bernd Thaller's Visual Quantum Mechanics1 and several others. I found the exercises in Physlet Quantum Physics to be more interactive and in some senses more engaging than in Thaller's work, although at a generally lower level. At the high school and nonscience major undergraduate level, the work of the Kansas State Physics Education Research Group is also of interest and is readily accessible (see

Improved Education

It's difficult to overstate the problem presented to the physics community in producing students who are adept mathematical problem solvers, but poor conceptual thinkers. Educational research by Eric Mazur 2 highlights this problem. The new conceptual frameworks we would like our students to build during our courses will always be built from their preexisting experiences. Physlets provide a way for students to gain virtual experiences and can supply part of the "scaffold" needed as students build these new frameworks. The book's authors previously presented many of the perceived advantages of the physlet approach elsewhere. In particular, faculty members considering using Physlet Quantum Physics might consider reading the authors' article on using physlets to teach thermodynamics. 3 The article contains the authors' own thoughts on the value of using the physlet approach to develop students' conceptual understanding of an unfamiliar topic.

Learning by Doing

The book's 200 exercises represent a reasonable breadth of difficulty levels, giving the instructor some flexibility to tune assignments to his or her individual course. A few minor limitations exist in some of the simulations, though. As Figure 1 shows, for example, the Rutherford scattering simulation lets the user vary the energy of the incident alpha particles, but at its lowest allowed limit of 2 mega-electron volts (MeV), the simulation stops before the alpha particles really begin to interact with the target nucleus. That said, most of the exercises are constructed with the student in mind and are easy to use. The coverage of time dependence in superposition states was a highlight of the exercises for me, and it's a topic too often glossed over in many introductory textbooks.


Figure 1   Rutherford scattering simulation. The user can vary alpha particles' energy, but at 2 mega-electron volts, the simulation stops, well before the alpha particles really start to interact with the target nucleus.

In a few places, awkward wording leaves the reader a little befuddled. An example is how the authors write problem 14.8 in the text, which deals with radioactive decay: "The graph fits the most for large amount of radioactive nucleus present." However, the reader shouldn't let these minor problems detract from what is overall a high-quality resource for instructors.

The exercises and simulations come from the authors' own pedagogical research and experiences as teachers. The authors' earlier works, Physlet Physics: Interactive Illustrations, Explorations and Problems for Introductory Physics (Prentice Hall, 2003) and Physlets: Teaching Physics with Interactive Curricular Material (Prentice Hall, 2000), concentrated on material suitable to the general introductory physics sequence, and this history might have been what produced a work that graciously spans the sophomore curriculum and reaches its fingers into upper-level courses.


The refrain to teach with technology has been a central theme on college campuses for the past decade, and perhaps it has been felt nowhere as profoundly as in the physical sciences. One of the questions in this debate has been whether technology should be used as a teaching tool, or if we should teach our students to use the technology. In this debate, Physlet Quantum Physics differs from Thaller's Visual Quantum Mechanics—the authors use Java for the simulations, and the source isn't readily available to the students, whereas Thaller chose to use Mathematica for the simulations in his book and includes the source at the click of a button. The use of Java rather than Mathematica or another proprietary application allows for easier deployment on a campus intranet and is less restrictive of the students' platform choice. I successfully used the software found on the accompanying CD-ROM on Macintosh OS X, Windows XP, and Solaris.

Overall, the question of whether to use a simulation as an illustration and virtual laboratory or to have students create their own simulations is a pedagogical choice for which good arguments exist on both sides. In my own opinion, there should be a transition from using simulations to creating them as students progress through the curriculum. In this way, the book's emphasis on sophomore- and junior-level material matches the authors' choice of approach well. I plan to incorporate several of the exercises in my own Modern Physics course.


About the Authors

James Brown is an assistant professor of physics at Wabash College. His research is in the experimental exploration of nuclear structure in extremely neutron-rich nuclei. Brown has a PhD in physics from the University of Michigan. He is a member of the APS and the American Association of Physics Teachers. Contact him at
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