Volume 32, Issue 2, February 1964
Index of content:
32(1964); http://dx.doi.org/10.1119/1.1970157View Description Hide Description
Prepared at the request of the AAPT Committee on Resource Letters; supported by a grant from the National Science Foundation.
This is one of a series of Resource Letters on different topics, intended to guide college physicists to some of the literature and other teaching aids that may help them improve course contents in specified fields of physics. No Resource Letter is meant to be exhaustive and complete; in time there may be more than one letter on some of the main subjects of interest. Comments and suggestions concerning the content and arrangement of letters as well as suggestions for future topics will be welcomed. Please send such communications to Professor Arnold Arons, Chairman Resource Letter Committee, Department of Physics, Amherst College, Amherst, Massachusetts.
Notation: The letter E after an item number indicates elementary level, useful principally for freshman liberal arts through sophomore physics courses; the letter I indicates intermediate (junior, senior) level; and the letter A indicates advanced material principally suited for senior, graduate study. An asterisk (*) indicates items particularly recommended for introductory study.
Additional copies: Available from American Institute of Physics, 335 East 45 Street, New York, New York 10017. When ordering, request Resource Letter Scy-1 and enclose a stamped return envelope. A small booklet containing reprints of some of the fundamental references will soon be available for purchase from the American Institute of Physics.
32(1964); http://dx.doi.org/10.1119/1.1970159View Description Hide Description
The ray-tracing method is used to discuss Gaussian optics. After proving that Gaussian optics can be described by matrices, some often-used general formulas for telescopic and focusing systems are derived. This formalism is then used to solve several problems. They are selected to make the reader familiar with the application of the matrix representation of Gaussian optics and to acquaint him with some optical systems that are very useful but not well known among physicists who use optical methods only occasionally.
32(1964); http://dx.doi.org/10.1119/1.1970138View Description Hide Description
A Mössbauer-effect apparatus, suitable for either lecture demonstration or inclusion in an undergraduate teaching laboratory, is described. Use of a rotating tilted disk to provide linear motion between source and absorber simplifies the construction and calibration of the experimental equipment. Some features are as follows: calibration of velocity by timing rotations of the wheel with a stopwatch, provision of a large-scale motion which graphically illustrates the first-order relativistic Doppler shift and its effect on monochromatic radiation, and sufficient precision to measure the nuclear Zeeman splitting in iron of the transition. Construction details, as well as instructions for the use of the equipment, are given.
32(1964); http://dx.doi.org/10.1119/1.1970139View Description Hide Description
A review of the chain of experiments whose results were finally explained by Compton's discovery of the Compton effect shows that these experiments were not solely in the field of x rays. The studies of the scattering of high-energy gamma rays of radium had presented physicists with the puzzle that scatteredgamma rays were distinctly less penetrating than were those that had not been scattered, and that the amount of this “softening” of the scatteredgamma rays was dependent on both the initial “hardness” of the gamma rays and on the scattering angle. Many of the experimental facts of the Compton effect were well known from the studies of scattering of gamma rays some years before the effects were observed with x rays. Compton's interest in the problem was apparently greatly stimulated by his own experiments on the scattering of gamma rays.
However, since the first detailed and convincing experimental verification of several of the consequences of Compton's hypothesis came from experiments with x rays, one may not be aware of the important role played by gamma-ray experiments in the steps leading to the discovery.
32(1964); http://dx.doi.org/10.1119/1.1970140View Description Hide Description
An experiment is described in which the magnitude and angle dependence of the wavelength shift of Compton scatteredphotons can be determined. The equipment necessary for the experiment is simple and inexpensive. The experiment is a modified version of the “absorption curve” type of study which as early as 1904 (nearly 20 years prior to Compton's discovery) showed the wavelength shift of scatteredgamma-rayphotons.
32(1964); http://dx.doi.org/10.1119/1.1970141View Description Hide Description
A description is given of an advanced laboratory experiment in which the student is able to verify the Compton effect in detail. The experiment allows the student to examine the angular dependence of the energy of the Compton-scattered photon and of the Compton-scattered electron. The simultaneity of the two scattered “particles” is the key to the experimental observations. The results allow one to directly verify conservation of energy for single-photon scattering events. The agreement of experiment and theory then allow one to conclude that momentum is also conserved in these encounters.
32(1964); http://dx.doi.org/10.1119/1.1970142View Description Hide Description
After a brief discussion of space inversion and time inversion, the distinction between magnetic and nonmagnetic crystal classes is illustrated by reference to cubic lattices. The appearance of “forbidden” effects in various crystal classes is discussed and recent experimental work on pyromagnetism, the magnetoelectric effect and piezomagnetism in antiferromagnetic materials is reviewed.
32(1964); http://dx.doi.org/10.1119/1.1970143View Description Hide Description
Assuming that the fields of a moving-point charge as computed from the retarded Liénard-Wiechert potentials give valid descriptions for moving electrons, it is shown that no net second-order static electric field of the type discussed by Rosser appears on the axis of a charge-neutral circular loop carrying a steady current. An argument is given for the nonexistence of such “residual” electric fields around any closed, charge-neutral region in which the current flow is time independent.
32(1964); http://dx.doi.org/10.1119/1.1970144View Description Hide Description
Transition probabilities for the forced, undamped quantum harmonic oscillator are obtained by expressing S-matrix elements entirely in terms of Heisenberg states and operators. The application of this method to this elementary-field theoretic model provides a simple example of the contraction technique of modern field theory whereby particles are converted into their corresponding currents. This problem was recently analyzed in the interaction picture from a pedagogical point of view and the treatment presented here is given in the same spirit.
32(1964); http://dx.doi.org/10.1119/1.1970145View Description Hide Description
A detailed study of the kinematics of neutron-proton, proton-neutron and neutron-neutron scattering (henceforth called n-p, p-n and n-nscattering, respectively) reveals a significant difference in the elastic differential cross section in laboratory directions corresponding to the near backward direction in the center of mass system. Based on the finite n-p mass difference, the n-pscattering cross section goes to ∞ at 86°59.5′, the p-nscattering shows a slight amount of backward scattering and the n-nscattering cross section equals zero for all laboratory angles greater than 90°. Most treatments of n-pscattering limit the discussion of the kinematics of the scattering process to a neutron-proton mass ratio to unity. It is of interest to consider the extent to which the actual difference in mass influences the angular distribution of the scattered particle. It is the purpose of this paper to discuss the consequences of the small, but non-negligible, n-p mass difference in the kinematics of scattering. Although it is not possible to obtain free neutrons at rest and hence p-nscattering cannot be observed in the laboratory, it, with n-nscattering is discussed here to get an idea as to what the kinematics of n-pscattering would have been if neutrons were lighter than protons and if the neutron mass were exactly equal to the proton mass.
32(1964); http://dx.doi.org/10.1119/1.1970146View Description Hide Description
A decomposition of the Lorentz transformation is considered which is thought to be more amenable to a simple physical interpretation than a similar type of decomposition given by Møller. While such decompositions are not unique, they can be of some value in considering the limiting processes by which one obtains the infinitesimal Lorentz and Galilean transformations.