UniServe*Science News, Vol. 5, November 1996

Understanding the Unobservable: A Reconstruction of First Year Quantum Physics

Andrew Cheetham, John Rayner, and Susan Bennett. School of ElectronicsEngineering and Applied Physics, University of Canberra

Understanding the Unobservable
is a Computer-Based Learning (CBL) package developed at the University of Canberra and designed to present first year quantum physics within an engineering context for students of electronic engineering and the physical sciences.

In traditional first year physics courses Quantum Physics is a notoriously difficult subject to teach at the introductory level. The main cause of difficulty is the non-intuitive, indeed in many respects counter intuitive, nature of many of the concepts presented. Traditionally this material is presented historically starting from Planck's explanation of black body radiation with applications such as lasers or semiconductors receiving cursory attention towards the end of the course. Unfortunately the conceptual framework of the material, and its vital importance to modern technology is usually lost in this approach. A further impediment to understanding, and even acceptance of the material, is that our students ask the question, why do engineers need to know or understand this? With quantum effects playing an ever increasing role in modern electronics it is vital that first year students not only understand this material but also appreciate its importance in electronic devices.

This course begins with a number of engineering applications, such as solarcells for solar powered cars, which all ultimately rely on the semiconductor pn-junction. Understanding the operation of the pn-junction provides the trigger for introducing quantum physics via photons and the photoelectric effect. The course then proceeds through a series of six further modules working through the material presented below to arrive back at the pn-junction where a detailed experiment is carried out on solar cells.

The package is divided into the following sections:

1: From Systems to the Subatomic.

2: Photons and Quantisation.

3: Atomic Spectra and Bohr Theory.

4: Further Quantum Effects and Implications.

5: Atomic Structure.

6: Energy Bands and Intrinsic Semiconductors.

7: Extrinsic Semiconductors and the p-n Junction.

An Interactive Multimedia format on CD-ROM was chosen for several reasons. It allowed us to show through animations the relationship between what was happening at the atomic level to the macroscopic observations. Additionalbenefits included the simulations of experiments, visualisation of mathematics,and the incorporation of practical applications as well as all the usual benefits of a self-paced, interactive presentation.

The project is now complete in that the package is being shipped to all Physics and Electronic Engineering departments in Australian universities. What remains to be carried out is an evaluation of the effectiveness ofthe course.

Andrew Cheetham

andrew.cheetham@canberra.edu.au





An example of a simulated experiment, in this case the photoelectric effect. Here the student can change the potential across the phototube using the slider at the bottom of the screen. As the potential is changed the current on the meter changes appropriately, the electrons flow in the tube (only if the light is turned on!) and the Current/Voltage graph is plotted. The student is asked to make certain observations for use later in the experiment.