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S. M. Simkin (Michigan State University)
Two spectroscopic ``mini-labs" or homework exercises suitable for an introductory level astronomy class have been developed using the public domain software of the MSU, LON-CAPA learning system (http://s10.lite.msu.edu/adm/about.html). These are accessible to registered students over the web and provide each student with a unique, personalized ``homework" set.
One of these, titled ``Fingerprinting the Elements," employs a set of optical, color, emission line spectra (generated from published wavelength-intensity tables). Spectra of several different elements, with slit configurations which are not shaped like lines, are then randomly selected and presented to the student for identification. This exercise not only reinforces the idea that emission-line spectra are unique signatures for each element but also graphically illustrates the fact that ``line-spectra" are not really formed from lines but are actual sequences of colors (photons at fixed frequencies or wavelengths).
The second homework module involves the more advanced concept of measuring Doppler shifts from absorption line spectra. In this exercise the student is provided with both an unshifted Balmer emission-line spectrum and an adjacent, unshifted Balmer absorption-line spectrum (each in true color), The student is then presented with randomly selected pairs of similarly plotted spectra in which the absorption line spectrum has been shifted (to the red or blue) by a known velocity. The goal is to determine the direction of motion (towards or away), measure the wavelength shift interactively, and calculate the velocity of the moving ``object." When initially presented as a homework set to ~230 non-science major college students, this latter exercise revealed a surprising result. Very few of the students were able to determine the DIRECTION of motion by looking at the colored spectra and measuring the offsets between the absorption and emission lines, although most of them ``knew" that a redshifted spectrum was generated by an object moving away from the observer. Thus the idea of a fixed, ``lab" reference frame was a critical missing element in their understanding of the Doppler shift.
Initial development of LON-CAPA was sponsored by Michigan State University with additional support by the National Science Foundation under NSF ITR 85921, the Andrew W. Mellon Foundation and the Alfred P. Sloan Foundation.
If you would like more information about this abstract, please follow the link to http://jabiru.pa.msu.edu/. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.
The author(s) of this abstract have provided an email address for comments about the abstract: simkin@pa.msu.edu
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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.