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Powerful Tools Require Careful Use
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John W. Moore
University of Wisconsin-Madison, Madison, WI 53706-1396 |
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This issue is out of print. |
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Both programs in this issue make very effective use of computer graphics and visualization to get their points across. A Window on the Solid State uses a large number of images of models of solid-state structures of metals to illustrate closest packing and other concepts needed by a student who wants to understand these structures. How a Photon Is Created or Absorbed includes three-dimensional surface plots generated by a spreadsheet and animations of the process of emission to help students understand what happens during a spectroscopic transition, why this results in absorption or emission of electromagnetic radiation, and why there are selection rules. Computer visualization is a powerful tool. Its very power implies that great care must be taken to use it appropriately. Strongly implanting incorrect or misleading images in students minds is probably worse than using hand-waving or fuzzily written descriptions that generate little real understanding. Something incorrect taught well will have to be unlearned later, and until it is may continually mislead students and make it more difficult for them to learn other concepts. Simply because sophisticated computer visualization tools are available does not mean that they will be used to best advantage pedagogically. I thought about this as I viewed some of the papers presented at the 13th Biennial Conference on Chemical Education held last summer at Bucknell University. In many cases graphics and visualization were used quite effectively, but in others there were artifacts of the visualization process that introduced what I considered to be misleading information. For example, one visualization showed a super computer calculation of ionization of a water molecule. As one OH bond stretched, the electron-density contours in the visualization suddenly jumped, implying a discontinuous change in electron density. When I raised this point with one of the authors I was told that this resulted from an artifact of the calculation and visualization methods and was not real. Nevertheless, the author did not consider it to be a problem for students. Maybe not, but I wonder. At some not too distant future time I expect to see an article or paper explaining why this observation in the computer visualization is real and indicating how we ought to teach it to students! Just because the latest, greatest visualization software creates a certain image or animation does not imply to me that that image is the best or most effective pedagogy. Every image or animation used in a multimedia presentation or interactive lesson needs to be considered carefully with regard to the impressions it creates especially those impressions not anticipated by the creator of the image or animation. Several examples come to mind based on programs in this or previous issues. The authors of How a Photon Is Created or Absorbed thought long and hard about the jumps that are seen in the isosurface animation of the 1s-2s transition for the hydrogen atom. The jumps occur because the isosurface is an electron density contour that encloses a certain percentage of the electron density. When that surface crosses the radial node in the hydrogen atom's 2s orbital, there is a large jump in the position of the contour and a corresponding discontinuity in the computer animation. Bob Rittenhouse, who created the visualization software, was well aware of this problem from the start, and his co-authors recognized it as soon as he described it. Giles Henderson experimented for some time with different ways of viewing the atom that might alleviate the problem. For example, Giles created a visualization in which there was a cutaway view of the isosurface, with a dot-density diagram inside. Eventually the authors and editors arrived at what you see in this issue: a dual visualization in which the isosurface and a dot-density diagram are both animated side by side. We (authors and editors) believe that this provides the best approach to the problem of presenting the electron density change in a way that is not misleading. The best hedge against introducing misleading or incorrect information graphically and powerfully is to have a large number of different people view what has been created and attempt to pick up on problems that have been missed by an author. That is where peer review, one of the hallmarks of JCE: Software, comes into play. We have an Editorial Board and a large number of reviewers as well as a knowledgeable staff. A subset of these evaluates every submission carefully. Authors make extensive changes before a submission is published, and the editorial staff contributes a great deal of expertise toward providing thorough and clear documentation that tells teachers and students how to use published software. All of this takes time and increases the cost of what is ultimately sent to our subscribers, but we believe that the final product is well worth the effort. The Guide to Submissions provides more information about the editorial and peer-review processes that we follow. Your comments regarding how they can best support dissemination of software that has maximum pedagogical usefulness are welcome at any time. |
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Last Updated: April 26, 2001 Created: December 3, 1996 |
Created by: J. L. Holmes Comments to: jceonline@chem.wisc.edu |
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| © 1997 Division of Chemical Education, Inc., American Chemical Society. All rights reserved. | |