PHYSICS 406

Possible Topics for Term Reports

The purpose of these reports if to help you find a particular, small piece of the subject of electromagnetism that interests you especially, and to give you a bit of a guide to push your knowledge further in that direction. Of course I want to encourage you to do that, as does the author of your text. Therefore, any such report, of reasonable quality, would constitute an addition to your final grade for the course, up to a maximum of 5% for a good report. In principle, you may even do two such reports, if you like, BUT not more. They should be well-constructed, with good calculations, {\bf typed}, and with good references.
I should add that what I am looking for is NOT a "book report" as you might have done in English class. Rather what I am looking for is some discussion of the premises and assumptions, some details of the relevant calculations, and some interesting and useful conclusions, in a form that would be suitable for presenting the material to a class of interested physics majors. Therefore, it should reproduce appropriate calculations from the references you find, filling in all details of the calculation if necessary, as well as answering important questions such as {\bf why did the author do this or that calculation}, what is the result intended to explain, etc.

Please turn your report in as early as possible, but certainly no later than classtime on 7 December.

Listed below are a number of possible suggestions for such a report, many of them taken from the comments, with references, that your text intersperses throughout the material, usually in the footnotes, taken from Chs. 7-12.
If you find one interesting, you should go and do a small "literature search," beginning, at least, with the information and references that I have listed here. You should investigate the particular subject, follow through the calculations, perhaps find some more relevant literature, and then write a small report on it, using the material from your references, being of course certain that you list all the references you find. You are welcome to talk to me, or your classmates, or even your friends---if you reference them properly---about the subject as you work on it.

Note that AJP below refers to the American Journal of Physics, a journal intended for beginning students of physics in universities.

The "jumping ring" described in Example 7.6 on p. 304 of Griffiths.
1. He gives a reference by Schneider and Ertel, AJP 66, 686 (1998).
Very long transmission lines and the problems related to the fact that one cannot transmit information about the current situation on any point at any speed faster than light.
This is related to Griffiths' (admittedly) inaccurate description of the way such lines work as given in Prob. 7.16, on p. 309. He suggests reading for a more realistic treatment
1. in Sect. 9.5.3 [Wave Guides],
2. and/or in J.G. Cherveniak, AJP 54, 946 (1986).
3. Also relevant might be Heald's work, AJP 54, 1142 (1986) and other references given there.
The Feynman disk paradox: described briefly in Griffiths, p. 359, footnote 4, and also footnote 7 on p. 361. See in particular the references given there:
1. The Feynman Lectures on Physics, Vol. 2, pp. 17-5
2. F.L. Boos, Jr., AJP 52, 756 (1984),
3. R.H. Romer, AJP 34, 772 (1966),
4. T.-C. E. Ma, AJP 54, 949 (1986),
5. N.L. Sharma, AJP 56, 420 (1988),
6. E.M. Pugh and G.E. Pugh, AJP 35, 153 (1967),
7. R.H. Romer, AJP 35, 445 (1967).
Thomson's dipole, a system with one electric charge and one magnetic charge (monopole): described briefly in Problem 8.12, on p. 362 of Griffiths. References given there are
1. I.Adawi, AJP 44, 762 (1976), and also Phys. Rev. D31, 3301 (1985),
2. K.R. Brownstein, AJP 57, 420 (1989).
What is the history of the search for magnetic monopoles, and why does one really care? Griffiths has several comments, the entirety of Section 7.3.4 on the subject, a problem or two, and
1. a reference for an extensive bibliography, namely A.S. Goldhaber and W.P. Trower, AJP 58, 429 (1990).
How the phenomenon of transparency occurs, as mentioned briefly on p. 383, Section 9.3 of Griffiths , with reference
1. M.B. James and D.J. Griffiths, AJP 60, 309 (1992).
Our discussions, modelled on Griffiths' Ch. 11, on radiation output from oscillating electric and/or magnetic dipoles will all be restricted to the situation where the length of the antenna is much less than the wavelength of the radiation being output. This is however not really the situation in most commercial transmitting antennas; therefore, a better understanding of how real antennas work could be quite interesting, more for the details than for any changes in the underlying metaphysics, of course. Some better discussion is, for instance, given in the following textbook:
1. Classical Electricity and Magnetism, A Contemporary Perspective, by V.D. Barger and M.G. Olsson (Allyn and Bacon, Inc., Boston), particularly Section 10-6B.
2. There are certainly more detailed "engineering handbooks" that may be consulted as well; I have a couple in my office, but many exist and fairly easily available.
A moderately-detailed understanding of how rainbows form, including the general reason---scattering by water droplets---the behavior of the primary bow, the secondary bow, and the dark band between the two could be quite interesting. Reasonable references could be
1. Classical Electricity and Magnetism, A Contemporary Perspective, by V.D. Barger and M.G. Olsson (Allyn and Bacon, Inc., Boston), particularly Section 9-4.
2. Another reference is an article in The Physics Teacher, by R.W. Robinett, 21, p. 388 (1983).
Group velocities, information velocity, signal velocity, precursor wave velocity, and others are all very interesting attempts to understand better the phenomenon of finite, pulsed waves through material. (All serious attempts to understand this involve the use of Fourier transforms in a serious way.) Some of the various ways to understand it are discussed briefly in Section 9.4.3 of Griffiths, along with the references given in footnote 14, on p. 399:
1. Waves, by F.S. Crawford, Jr. [McGraw-Hill, New York, 1968], especially Section 6.2
2. S.C. Bloch, AJP 45, 538 (1977),
3. P.C. Peters, AJP 56, 129 (1988),
4. and also the rather advanced book by Brillouin
Evanescent waves are very intriguing, related to quantum-mechanical tunnelling through barriers. A single problem is given concerning them, Problem 9.37, on p. 413 of Griffiths, along with the reference in footnote 19, on p. 414. Much more interesting, although somewhat more complicated is what happens when one considers not just a single, monochromatic wave, but a more-physical wave packet, when the Goos-Hanschen shift is involved, causing a shift of the place where the wave packet enters the third medium, relative to what straight-line optics would expect. I will need to find a reasonable reference for it.
1. F.Albiol, S. Navas, and M.V. Andres, AJP 61, 165 (1993).
2. the webpage at http://en.widipedia.org/wikj/Evanescent_wave
3. recent article on the Goos-Hanschen shift and evanescent wave coupling, in {\it Europhysics Letters}, 57(2), p. 191 (2002)
4. quite interesting actual photographs of shifts of Gaussian beams in {\it Physical Review E}, 62, 7381-7388 (2000).
The physical understanding of the so-called "Coulomb gauge" is an intriguing problem. It is briefly mentioned in 10.1.3, on p. 421, and a reference is given in footnote 1 on that page, while there is another related reference on p. 542. The gauge transformation referred to there is quite interesting, but a little bit complicated.
1. O.L. Brill and B. Goodman, AJP, 35, 832 (1967).

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finley@tagore.phys.unm.edu		Last updated/modified: 15 October, 2006