bluuebunny/crossref_metadata_2025 huggingface dataset:
Some basic properties of stimulated and spontaneous emission: A semiclassical approach
Authors: Durrant A. V.
Published: March 2005

The coherence and directional properties of stimulated and spontaneous emission can be understood without a knowledge of quantum electrodynamics. This paper presents a semiclassical description of the interaction between a free atom and a weak optical field under conditions of either a stimulated emission or a stimulated absorption resonance. It is shown that, under certain conditions, the stimulated or spontaneous radiation fields emitted from a sample of atoms will propagate in the same direction as the incident beam, will be coherent with the incident beam, and will have the correct phase to provide amplification or attenuation.
Simple experiment to introduce the photomultiplier
Authors: Burns Donal J. , Reynolds James M.
Published: March 2005

A simple experiment using an inexpensive RCA 931A photomultiplier is described. This experiment is performed in an elementary physics laboratory and makes a measurement of the secondary electron emission coefficient at the last dynode.
Co-teaching experiment at the University of Rhode Island
Authors: Kirwan Donald F. , Willis Jack
Published: March 2005

The employment of a co-teaching approach in the calculus-based, first-year, elementary physics courses has caused many favorable comments by both faculty and students. Student questionnaire responses are presented along with a discussion of the techniques, pitfalls, and advantages of this method of classroom instruction.
An exact relativistic solution of the classical spin precession in a constant magnetic field
Authors: Crater H.
Published: March 2005

An exact solution is given for the precessional motion of the spin four-vector S in a constant magnetic field based on the covariant equations of Bargmann, Michel, and Telegdi. Its relation to the nonrelativistic solution is explicitly demonstrated.
Scalar and pseudoscalar charges
Authors: Frankel Sherman
Published: March 2005

The interaction of a ’’scalar’’ charge es (even under T) and a ’’pseudoscalar’’ charge ep (odd under T) is investigated in the framework of classical mechanics. We show that the most general force consistent with the conservation of linear momentum and angular momentum is F=esep(r×v)/cr3, where c is a constant. This is just Dirac’s force between electric and magnetic charges. No use is made of Maxwell’s equations. With the single assumption that the forces can be expressed in terms of vector and axial vector fields, we can derive exact expressions for the fields and then for the forces between two scalar and two pseudoscalar charges. These forces, in turn, are found to be identical with those of Coulomb and Biot–Savart. The theory retains P conservation and T invariance in both Newton’s laws of motion and the expressions for the fields.
Perturbation expansion of the Dirac equation
Authors: Seitz W. A. , Matsen F. A.
Published: March 2005

Applying perturbation theory to the Dirac Hamiltonian yields eigenvectors that account for spin effects such as Zeeman and spin–orbit splitting. (AIP)
Introductory experiment to determine the thermodynamic efficiency of a household refrigerator
Authors: Bartlett Albert A.
Published: March 2005

An experiment is described in which students in an introductory laboratory can determine all of the relevant energy flows (and hence the coefficient of performance) of an ordinary household refrigerator and can compare their measured results with the coefficient for an ideal Carnot refrigerator operating between the same two temperatures. The analysis of the data makes use of the first and second laws of thermodynamics and the relationship for thermal conductivity. The experiment has relevance in the world of the energy crisis.
Conditions on wave functions derived from operator domains
Authors: Jordan Thomas F.
Published: March 2005

Conditions on wave functions that are eigenvectors often have a mathematical rather than a physical basis; they are required simply because an eigenvector of an operator must be in the domain of that operator. This is illustrated with derivations of the conditions at the origin on eigenvectors of a nonrelativistic Hamiltonian, for example, for the hydrogen atom or harmonic oscillator, and the condition that eigenfunctions of the angular momentum Lz must be single valued or continuous around a complete circle.
Nonrelativistic rotating charged sphere as a model for particle spin
Authors: Young Ralph H.
Published: March 2005

The rotating charged sphere is discussed as a model for particle spin. The nonrelativistic classical mechanics of the model shows a close analogy to the nonrelativistic (Pauli) quantum mechanics of spin. The spin contribution to the Hamiltonian operator, −γŝ⋅B (standard notation), represents the nonconstant part of the kinetic energy associated with spin. Variations of translational kinetic energy in an inhomogeneous static magnetic field are offset by variations of spin kinetic energy. The latter, along with the torque term responsible for them, cannot be overlooked without forfeiting conservation of energy.
Introductory biophysics course: Presentation of physics in a biological context
Authors: Henderson B. J. , Henderson M. A.
Published: March 2005

An introductory biophysics course for science students who have previously taken two quarters of noncalculus physics is described. The goal of the one-quarter course is to teach the students to use physics as a tool for understanding biological systems. Material covered emphasizes the physical principles of sound, light, electricity, energy, and information. Student response is favorable.
PSI for low-enrollment junior–senior physics courses
Authors: Frahm Charles P. , Young Robert D.
Published: March 2005

We have recently completed the preparation of PSI materials (study guides and unit tests) for seven junior–senior level physics courses: Mechanics, Electricity and Magnetism, Atomic Physics, Mathematical Physics, Physics and Computers, Astrophysics, and Relativity. Three additional courses—Solid State Physics, Nuclear Physics, and Quantum Physics—have been prepared by our colleagues. These are all elective courses at our institution and tend to have relatively low enrollments. By preparing them in the PSI format we are able to offer all ten courses every semester for any number of students with efficient use of faculty. A description of our materials, our mode of operation, and the reactions of students, faculty, and administrators are presented.
PSI general physics in a small community college
Authors: Gash Philip W.
Published: March 2005

This paper describes a PSI general physics course taught within the constraints of a small community college. The PSI format is described and student opinions of it are presented. The final exam grade distributions and the percentage of students completing the course are presented for the two semesters the course was conventionally taught, and for the two semesters the course was taught by PSI.
Principle of inertia in the Middle Ages
Authors: Franklin Allan
Published: March 2005

Perhaps the most significant change in the transition from Aristotelian or medieval science to classical or Newtonian mechanics is the change from the Aristotelian view of ’’Omne quod movetur ab alio movetur’’ (’’All that is moved is moved by something else’’) to Newton’s first law or the principle of inertia that ’’Every body continues in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed on it’’ [I. Newton, Principia (Univ. of California Press, Berkeley, 1960), Motte’s translation revised by Cajori, p. 13]. In this paper we shall show that this is not a sudden change but rather that it has a long and detailed history in the medieval critiques of Aristotle’s physics. The treatment of the problems of motion in a void, projectile motion, falling bodies, and the inclined plane by medieval scientists makes this transition quite understandable.
Diffusion coefficient for a Brownian particle
Authors: Harris S.
Published: March 2005

This paper utilizes several existing techniques in nonequilibrium statistical mechanics (in a new context) to provide a relatively simple and short evaluation of the diffusion coefficient for a Brownian particle.
Natural units via linear algebra
Authors: Maksymowicz Alexander
Published: March 2005

A systematic procedure is presented for introducing natural units, in which physical constants such as the speed of light in vacuum, Planck’s constant, and the mass of the electron are set equal to unity. The dimensions of physical quantities are represented by vectors in an abstract linear vector space, referred to as the dimension space. The quantities chosen as basic units play the role of basis vectors in this space. Conversion from one system of basic units to another corresponds to a different choice of basis vectors. Such a conversion is equivalent to a linear transformation on the dimension space and may be implemented by matrix multiplication. A detailed treatment is given of the transformation from mass–length–time units to a system of natural units appropriate to the atomic domain. The broader applicability of linear algebra techniques to dimensional analysis is briefly indicated by way of conclusion.
A simple model to explain the slowing down of light in a crystalline medium
Authors: Kunz Kaiser S. , Gemoets Ernesto
Published: March 2005

Two main questions arise when one seeks to explain the propagation of light in a dielectric medium: (i) Why does the wave slow down? (ii) Why is there apparently only a forward wave? There is a subtle answer to these questions provided by the Ewald–Oseen extinction theorem, but the physical mechanism involved is not very easily visualized. This article sets forth a simple one-dimensional model of parallel polarizable slabs that makes the mechanism clear and links the two questions in an interesting way.
One more derivation of the Lorentz transformation
Authors: Lévy-Leblond Jean-Marc
Published: March 2005

After a criticism of the emphasis put on the invariance of the speed of light in standard derivations of the Lorentz transformation, another approach to special relativity is proposed. It consists of an elementary version of general group-theoretical arguments on the structure of space–time, and makes use only of simple mathematical techniques. The principle of relativity is first stated in general terms, leading to the idea of equivalent frames of reference connected through ’’inertial’’ transformations obeying a group law. The theory of relativity then is constructed by constraining the transformations through four successive hypotheses: homogeneity of space–time, isotropy of space–time, group structure, causality condition. Only the Lorentz transformations and their degenerate Galilean limit obey these constraints. The role and significance of each one of the hypotheses is stressed by exhibiting and discussing counterexamples, that is, transformations obeying all but one of these hypotheses.
Probabilistic approach to teaching the principles of quantum mechanics
Authors: Santos Emilio
Published: March 2005

A new approach to teaching the principles of quantum mechanics is presented that leads quickly to the Hilbert space postulates. After convincing the reader that an algebra of observables is a useful way to describe probabilistic observations, the paper introduces an evolution operator and demonstrates that it cannot commute with position observables. This fact, plus elementary assumptions about the possible form of the evolution operator, are sufficient to demonstrate that, if the deterministic limit of the theory is to yield Newton’s law, the evolution operator must have the familiar form of the Hamiltonian: essentially kinetic energy plus potential energy.
Classical particles in quantum mechanics
Authors: Patsakos George
Published: March 2005

An analysis of the change in the concept of a particle required by the passage from classical to quantum theory suggests a ’’classical particle representation’’ for the latter which should allow purely quantum-mechanical results to be cast into a form suited to interpretation in semiclassical terms. Application of this representation to the examples of the free particle and the particle in a constant force field essentially reproduces the usual arguments as to how classical trajectories can be generated in the quantum theory, although from a somewhat different point of view than that usually presented. Applying the representation to the energy eigenfunctions of the one-dimensional harmonic oscillator provides an interesting semiclassical interpretation of these functions and their relationship to the quantization rules of the old quantum theory. Some speculations regarding other possible applications of this approach are also presented.
Teaching physics for related sciences and professions
Authors: French A. P. , Jossem E. L.
Published: March 2005

This paper describes a conference held in the Summer of 1976 concerning the teaching of physics for those who make use of physics in other disciplines or fields of activity. An appendix contains the set of reports prepared during the conference by working groups formed to consider the problems of relating physics to various specific disciplines.
1973–1974 student credit hour production in eight public Illinois physics departments
Authors: Baldwin Thomas O. , File Dorothy M.
Published: March 2005

Student credit hour (SCH) production data for physics departments in state institutions in Illinois for the 1973–1974 academic year have been compiled. Full-time equivalent (FTE) faculty have been calculated and compared with actual numbers under the assumption that each department would be required to produce the same number of SCHs/FTE. Implications for present staffing patterns and problems of maintaining faculty size are discussed.
Coupling of an odd particle to a deformed core
Authors: Das Gupta S. , de Takacsy N.
Published: March 2005

Band-mixing and decoupling factors are obtained for the coupling of an odd particle to a deformed core. The derivation avoids the use of commutation rules in a rotating frame and is easily generalized to more microscopic models of deformed nuclei.
The five forms of Laplace’s cosmogony
Authors: Jaki Stanley L.
Published: March 2005

Between 1796 and 1824, Laplace published five forms of his theory of the origin of the solar system—a fact ignored in the literature on Laplace and cosmogony. Yet, those five forms not only reveal Laplace’s undue fondness for his theory, but also give a glimpse of his biased handling of recent discoveries in astronomy and of his reluctance to test in a quantitative manner some grave dynamical problems implied in his theory, later called the nebular hypothesis.
Fresnel zone plate: Anomalous foci
Authors: Higbie J.
Published: March 2005

It is found that, when a zone plate is examined in practice, foci exist where there should be none. An approach is developed which reveals that the zone plate is a circular diffraction grating, which in turn explains how a hologram works in a very direct manner.
Rotating water sprinkler
Authors: Weyland J. A. , Patterson J. D.
Published: March 2005

We calculate the range R of a rotating water sprinkler as a function of the angles ϑ,φ specifying the orientation of the nozzles, the mass rate of water ejection, and the area of the orifice of the nozzles. In order to compare the two approaches, we solve the problem completely in both a laboratory and a rotating frame of reference. We discuss advantages and disadvantages presented by each reference frame in solving the problem. We display R (ϑ,φ) in three-dimensional plots, treating water ejection rate and nozzle orifice area as fixed parameters.
On fundamental equations for thermodynamic systems
Authors: Hajj Fuad Y.
Published: March 2005

The principle of maximum entropy and the principle of minimum energy lead to inequalities which are useful in testing the validity of fundamental equations. It can be seen that these principles are actually conditions on the curvature of functions containing the variables S, U, V, and n. Several theorems illustrating the nature of these functions are proved by simple methods. The condition for the equivalence of the two principles is shown.
The San Luis project: An attempt to decentralize physics in Mexico
Authors: Will T. A. , Valladares A. A.
Published: March 2005

The overwhelming concentration of physics activity in Mexico City, resulting in a ’’brain drain’’ from other parts of the country, has led to a number of efforts designed to decentralize the Mexican educational and research establishments. We evaluate here one such project, established in June 1972 at the University of San Luis Potosí and continuing at present. Begun primarily as a modest research effort, in its present—and most successful—phase, intensive core graduate level courses are given in San Luis Potosí by visiting professors. Although the results of the project have not met our optimistic expectations, a nucleus of dedicated physicists has been formed, and the competence of local teachers has increased.
Diffraction in time and the time–energy uncertainty relation
Authors: Moshinsky M.
Published: March 2005

The purpose of this paper is to discuss two forms in which the time–energy uncertainty relation can appear. One of them concerns the time of preparation of a given state and the other the lifetime of compound systems. Both will be illustrated here through exactly solvable examples. The first one will be the opening and subsequent closing of a shutter on which we have an incident beam of particles. This problem shows a diffraction-in-time effect closely connected with the first type of time–energy uncertainty relation. The second will be the decay of a compound state described through a schematic R matrix formalism. There one can clearly see the transition between the time–energy uncertainty relation as associated with the interval in which the decay process has been in operation, and as associated with the lifetime of the compound state.
Partial derivatives, the energy crisis, and urban transportation: Calculus for concerned citizens
Authors: Bent Henry A.
Published: March 2005

The energy crisis and issues concerning urban transportation offer teachers of physics opportunities to illustrate the meaning of partial derivatives and the principal relations among them with environmentally interesting examples based on commonsense arithmetic.
Alternate formulation of electron–photon interactions in relativistic quantum mechanics
Authors: Ruei K. H.
Published: March 2005

In this paper, we develop an alternate formulation of the electron–photon interaction in the framework of ordinary relativistic quantum mechanics (without second quantization). We use the Dirac equation of motion to recast the current density in a form linear in the photon wave function. This enables us to take the photon as the system and, regarding the electron as an ’’external field,’’ to iterate the photon wave equation by the standard method. In particular, we deduce the second-order matrix elements of Compton scattering, pair annihilation, and pair creation. The results so obtained are, of course, identical with those of the usual formulation, where the electron is taken as the system and the radiation is treated as the external field. The present approach complements the usual one; together, the two approaches reveal the symmetry of quantum electrodynamics under interchange of source and field.
Linearity of the Lorentz transformation
Authors: Baird L. C.
Published: March 2005

The Lorentz transformation is derived without an a priori assumption that it is linear, differentiable, or continuous. We do assume the invariance of Newton’s first law and order invariance of a sequence of events on a ray of light. The calculations are somewhat simplified by the use of so-called ’’temporal coordinates.’’
Experimental statistics for undergraduates. I
Authors: MacLeod A. M. , Ledingham K. W. D. , Morton W. T.
Published: March 2005

A description is given of an experiment to demonstrate the buildup of Poisson distributions with very high precision. Mean values up to 100 can be obtained, which enables a critical comparison of distributions with different means. By using small numbers of sampling periods, it is also possible to show how the means are themselves distributed, and to show that the standard deviation of the means is equal to σ/N1/2, where σ is the standard deviation of the ’’infinite’’ distribution and N is the number of sampling periods. Dead-time effects are also investigated experimentally.
Galileo and the fall of Aristotle: A case of historical injustice?
Authors: Casper Barry M.
Published: March 2005

Galileo’s case against Aristotle’s description of freely falling objects is presented. Possible alternative interpretations of Aristotle’s views are discussed.
Simple derivation of the Maxwell stress tensor and electrostrictive effects in crystals
Authors: Juretschke H. J.
Published: March 2005

Local equilibrium and energy considerations in an elastic dielectric crystal lead to a simple derivation of the Maxwell stress tensor in anisotropic dielectric solids. The resulting equilibrium stress–strain relations in the presence of electric fields are applied to determine the deformations of a charged parallel plate capacitor and to find the strains in the capacitor electrodes that accompany the charging.
Mechanical treatment of chemical, osmotic, and electrochemical equilibrium
Authors: Lunelli Bruno
Published: March 2005

Chemical, osmotic, and electrochemical equilibria are treated using the virtual work principle. This approach provides a unified view of these phenomena which is didactically very convenient, especially when the students’ curriculum schedules an early course of classical mechanics.
Normalization of states in perturbation theories
Authors: Bès D. R. , Dussel G. G. , Sofía H. M.
Published: March 2005

Simple expressions are given for the normalization coefficients in Rayleigh–Schroedinger, Brillouin–Wigner, and Bloch–Horowitz perturbation methods. These expressions are derivatives of the energy, or of the matrix elements of the effective Hamiltonian.
Kinetic theory paradox
Authors: Finucan Henry M. , Higbie J.
Published: March 2005

The mean time between collisions for a molecule in a gas is τ. However, when the molecule is observed at random, it is found that the mean time between collisions is 2τ.
Momentum of light in a refracting medium
Authors: Wong Hung-Kit , Young Kenneth
Published: March 2005

It is pointed out that neither Minkowski’s nor Abraham’s proposal gives correctly the momentum density of light in a refracting medium. The correct result due to Peierls is simply derived. The imbalance of momentum flux at an interface corresponds to a force on the surface, and this is contrasted with a delayed force due to a finite beam width.
Mathematical statistics in student physics laboratories
Authors: Szydlowski Henryk
Published: March 2005

Problems related to the modernization of the experimental procedure are considered based on the author’s experience as head of the physics majors’ laboratory. The curriculum for our freshmen has been modified to include, in the first semester, a lecture course and blackboard exercises in measurement theory largely comprising elements of mathematical statistics. Wortk in the physics laboratory during the second and third semesters has been made to include, to a much higher degree than hitherto, the elements of mathematical statistics. Statistical methods of measurement designing and experimental results evaluation are applied. As a rule, standard deviations as well as correlation and regression factors are determined, and the testing of statistical hypotheses is required. Conclusions from the experience gained are discussed briefly.
Derivation of noise formulas using Campbell’s theorem
Authors: Mathieson E.
Published: March 2005

Campbell’s theorem evaluates the mean-square fluctuation in the output of a system whose input is subject to a random succession of equal strength impulses. It is pointed out that this important theorem may be conveniently employed as the basis for a brief discussion of electrical noise in an undergraduate physics course. Practical formulas are derived to describe certain shot-noise situations. By using a specific conduction model, it is shown how Campbell’s theorem may also be applied to obtain thermal-noise formulas.
Transport approach to one-dimensional quantum scattering
Authors: Tikochinsky Yoel
Published: March 2005

Starting from ’’first principles,’’ transport and invariant imbedding equations are derived for one-dimensional quantum scattering. The connection between the two kinds of equations is established by means of a simple transformation.
What is the principle of equivalence?
Authors: Ohanian Hans C.
Published: March 2005

The strong principle of equivalence is usually formulated as an assertion that in a sufficiently small, freely falling laboratory the gravitational fields surrounding the laboratory cannot be detected. We show that this is false by presenting several simple examples of phenomena which may be used to detect the gravitational field through its tidal effects; we show that these effects are, in fact, local (observable in an arbitrarily small region). Alternative formulations of the strong principle are discussed and a new formulation of strong equivalence (the ’’Einstein principle’’) as an assertion about the field equations of physics, rather than an assertion about all laws or all experiments, is proposed. We also discuss the weak principle of equivalence and its two complementary aspects: the uniqueness of free fall of test particles in arbitrary gravitational fields (’’Galileo principle’’) and the uniqueness of free fall of arbitrary systems in weak gravitational fields (’’Newton principle’’).
A low-cost experiment in plasma physics for the advanced undergraduate lab
Authors: Maclatchy C. S.
Published: March 2005

A quantatative experiment in plasma physics requiring only a modest investment is presented. The plasma source is a seeded propane flame. The object of the experiment is to measure the characteristics of a cylindrical Langmuir probe and the ion density in the flame plasma.
Benjamin Franklin as experimental philosopher
Authors: Devons Samuel
Published: March 2005

The incomparable Benjamin Franklin, man of innumerable parts, pioneer of countless enterprises, set the stamp of his whole inimitable personality on all his works. A singular combination of pragmatism and idealism, of the practical and the philosophical, informed and inspired alike his business, his politics, his personal life, his experiments, and his science. Franklin’s contributions to science, and his electricity in particular, are here presented as illustrative of the exceptional talent and unique personality of this foremost experimental philosopher.
The Fizeau effect: Theory, experiment, and Zeeman’s measurements
Authors: Lerche I.
Published: March 2005

We have reconciled the apparent differences between the many theoretical formulas proposed over the years which purport to account for the speed of light in a moving medium being different from in a stationary medium. The majority of the differences arise from an imprecise definition, or use, of wavelength. A few of the formulas proposed are wrong and the errors are illustrated. We then appraise the basic experimental setup designed to measure the Fizeau effect pointing out the fundamental physical limitations inherent in the experiment and describing the sources of random experimental error. (There are always possible systematic errors about which we can say, or do, little.) In the light of the above analyses, we then consider the accuracy of the experiments reported by Zeeman—who is nearly always quoted as having performed the decisive experiments on the dispersive term in the Fizeau coeficient. We show that the minimum errors in his experiments are sufficient to rule out his capability for distinguishing experimentally between the competing formulas of Fresnel and Lorentz for the Fizeau effect; and, besides, the flow pattern Zeeman used was highly turbulent while the theory is known only for laminar flow. We suggest that the dispersive term in the Fizeau coefficient has not yet been accurately measured and we urge repetition of the experiment.
Evolution of the black-body spectrum in the Friedmann universe
Authors: Cooke James H.
Published: March 2005

A fully rigorous, but simple, derivation of the evolution of an initially black-body spectrum in the closed Friedmann universe is given. Some authors have assumed that, strictly speaking, one cannot speak of thermal equilibrium of the radiation, since it is in a changing gravitational background. This is shown to be incorrect, and a simple analogy of vibrations on an expanding circle of string illustrates the reason. It is possible to define a very natural dimensionless equilibrium constant. Finally, the problem of finding the electromagnetic eigenmodes is solved efficiently with differential forms.
Free electron motion in a plane electromagnetic wave
Authors: Hagenbuch Keith
Published: March 2005

The relativistically correct equations of motion for a ’’free’’ electron in a plane electromagnetic wave are written down including radiation damping. Iteration is used to obtain first, the exact solutions neglecting radiation damping, then, corrected solutions including radiation damping. It is seen that without radiation damping the electron will not experience forward acceleration caused by ’’radiation pressure.’’ With radiation damping included, the (constant) acceleration caused by radiation pressure is clearly seen. The effective cross section for the transfer of momentum to the electron is just the Thompson cross section. A ’’Compton formula’’ is obtained that is seen to have the same angular dependence as the ordinary Compton formula. The significance of the Compton formula is then perceived not to lie in its angular dependence, but in its wave independence.
PSI: A survival study
Authors: Bauer Rick
Published: March 2005

The Personalized System of Instruction (PSI) is probably the most widely used recent innovation in physics teaching. While much has been written about its ’’educational effectiveness,’’ little is known about the survival of PSI courses after they are introduced. In a study of particular interest to the readers of the American Journal of Physics, we examined the survival of all 12 PSI courses reported in the Journal through 1975. Seven of the 12 were still being taught. The experience of those who introduced these courses is used to provide background for teachers thinking of adopting the method and to give perspective on the survival of PSI as an innovation.
Heisenberg theory of ferromagnetism: constant coupling revisited
Authors: Brown H. A.
Published: March 2005

The Heinsenberg theory of ferromagnetism has been treated by many types of approximations; one of the more successful is known as constant coupling. The literature contains several different ways of arriving at results like those of the constant-coupling approximaion, but proofs that they are indeed equivalent are lacking in some cases. It is shown that two of these methods are equivalent for spin 1/2 and explicitly demonstrated that both yield exactly the constant-coupling results, though simpler in use and concept than the latter. Finally, it is shown that one of the two methods yields the same Curie temperatures as constant coupling for all spin.
Paradox and resolution in electrostatics
Authors: Ball James S. , Price Richard H.
Published: March 2005

A closed conducting surface possessing both conduction electrons and muons is hypothesized. A simple and persuasive proof is given, entirely in the framework of classical electrostatics and Newtonian gravity, to show that the region interior to such a surface is shielded from gravity. The resolution of the paradox is explained and a solution is given for the gravitational and electrostatic forces inside a spherical surface of the type hypothesized.
Results of a remedial laboratory program based on a Piaget model for engineering and science freshmen
Authors: Gerson Robert , Primrose Russell A.
Published: March 2005

Engineering and science freshmen who enter our institution with algebra deficiencies have a very low probability of performing satisfactorily in the required college-level calculus course. Two years ago, a remedial one-semester program was conducted for 36 freshmen who were identified by an entrance examination as being weak in algebra. The course was based on the assumption that the students were ’’concrete’’ in the Piagetian sense. The main part of the course required a general physics laboratory that provided selected experiences to bridge the concrete–formal gap. After three semesters, 31% of the participants in the course were receiving grades of C or above in calculus courses, as compared to 16% of those students who did not take the remedial program.
Particle spectrum
Authors: Corben H. C.
Published: March 2005

Data on elementary particle states are analyzed in a way that makes a number of regularities apparent. It is helpful to use a mass unit of approximately 1050 MeV, in terms of which the masses of a number of series of meson and baryon states can be represented approximately by M2=J+const, where the constant is characteristic of a particular series. Individual series exhibit a remarkable regularity in the signs of space parity, G parity, I spin, charge conjugation parity, and relative signs of resonant amplitudes.
Response of the Oersted Medalist
Authors: Crane H. Richard
Published: March 2005

E d i t o r’s note: Remarks made by H. Richard Crane upon receipt of the 1976 Oersted Medal. Bestowed by the American Association of Physics Teachers ’’for notable contributions to physics education,’’ the Medal was presented to Professor Crane at the ceremonial session of the joint meeting of the American Physical Society and the American Association of Physics Teachers, Chicago, Illinois, 7–10 February 1977. [See J. B. Guernsey, Am. J. Phys. 45, 507 (1977), for remarks made in presenting the Medal.]
Testing the mastery concept of self-paced learning in physics
Authors: Putt Graeme D.
Published: March 2005

An established course in introductory physics presented according to traditional and Keller plan methods of instruction has been used to study the mastery concept of the self-paced learning method in physics education. The results show that many more students can achieve ’’mastery’’ in a self-paced course than in a traditional course.
L. D. Landau’s plain talk to students of physics
Authors: Lifshitz E. M.
Published: March 2005

This article was published in 1971 in the Russian journal Science and Life. Teachers and students who read our Journal can profit from the advice of this master theoretician. We are grateful to E. M. Lifshitz and the editor of Science and Life for permission to publish the article and particularly to J. George Adashko for preparing the translation.
Nuclear collective model in two dimensions
Authors: Bouten M. , Van Leuven P.
Published: March 2005

The analogs in two-dimensional space of Bohr and Mottelson’s model can be used for the purpose of explaining simply the mathematics of nuclear collective motion, while conserving the essential physical ideas.
Binomial aspects of radioactivity
Authors: Ruby Lawrence
Published: March 2005

On the basis of a probability equation approach, radioactivity is shown to be a binomially distributed process, for any value of the observation time. The approximations necessary to establish the validity of Poissonian statistics are discussed.
A simple field theoretic description of photon interference
Authors: Walls D. F.
Published: March 2005

A description of photon-interference experiments of the Young’s type using the techniques of quantum-field theory is presented. In particular, an explicit illustration of Dirac’s statement that a photon interferes only with itself is given. The interference patterns produced by a one photon, an n photon and a coherent photon field are calculated. A discussion of the degree of optical coherence possessed by the above fields is also incorporated. by the above fields is also incorporated.
A simple demonstration on the freezing of the rotational energy of molecular hydrogen
Authors: Junod A. , Muller J.
Published: March 2005

The specific heat Cv of the diatomic gas H2 decreases from 5R/2 at room temperature to ∠3R/2 at liquid N2 temperature, a value typical of the translational energy only. This quantum effect can be shown in a quickly performed lecture demonstration, based on the principle of a differential H2/N2 acoustic thermometer.
Superposition of the radiation from N independent sources and the problem of random flights
Authors: Merzbacher E. , Feagin J. M. , Wu T-H.
Published: March 2005

It is often stated that the intensity of the signal produced by superposition of N equally intense, but randomly phased, monochromatic coherent waves tends to N as N becomes large. An examination (first made by Rayleigh) of the distribution of intensities obtained by superposing N independent monochromatic waves shows that the mean intensity is N and the variance is N2−N. Exploiting the analogy of this problem to random walk in two dimensions (’’random flight’’), we have recalculated the distribution for N=2 to 6 and compared it with the results from a computer experiment.
Electromotive force, potential difference, and voltage
Authors: Page Chester H.
Published: March 2005

Technical journals and dictionaries exhibit no uniformity regarding use of the terms electromotive force, potential difference, and voltage. Electromotive force is sometimes deprecated, and sometimes considered to be a synonym for one of the other terms. The three terms relate to different aspects of electrical phenomenona, and it is useful to draw distinctions among them and define each in a precise way.
Acceleration and weight of extended bodies in the theory of relativity
Authors: Gro/n O/.
Published: March 2005

A spring weight used as an accelerometer and as a dynamometer is considered. It is shown that in the theory of relativity the force scale of a dynamometer moving in a gravitational field is conventionally changed with position and velocity. Investigating the acceleration and weight of extended bodies, it is concluded that this weight does not depend on the position of the supporting force on the body. The connection between this result and the relativistic interpretation of the gravitational Doppler effect, which implies that from a global point of view the energy of a photon moving in a gravitational field is constant, is emphasized.
Motion of extended charges in classical electrodynamics
Authors: Levine H. , Moniz E. J. , Sharp D. H.
Published: March 2005

The Lorentz–Dirac theory of radiation reaction on the motion of point charges is beset by the well known problems of runaway solutions and preacceleration. We examine the classical theory of extended charged particles and obtain a differential-difference type equation of motion. Analysis of this equation reveals that the theory is internally consistent (i.e., no runaways or acausality) whenever the size of the particle exceeds the classical radius (defined as the radius for which the electrostatic self-energy equals the mass of the particle). A specific example is presented which explicitly shows the different character of the extended and point charge solutions.
Self-paced introductory physics course—An eight-year progress report
Authors: Brown G. C. , Greisen K. I. , Sievers A. J. , Naegele C. J.
Published: March 2005

In this article, we describe a self-paced, mastery-oriented introductory physics course which handles an enrollment of 600 students per semester. The format of the course includes some of the features of both the Personalized System of Instruction (PSI) and audio–tutorial instruction. We discuss the two-year transition period from a standard format to the self-paced format and identify the early problems associated with the new format as well as our solutions to these problems. We also estimate the cost of converting to and maintaining a self-paced format. We list some of the advantages and disadvantages of the format. Assessment of this self-paced course, which has now been in full-scale operation for six years, has been and continues to be positive.
Behavior of a soft spring
Authors: Heard Thomas C. , Newby Neal D.
Published: March 2005

An experiment is described which studies the dynamical behavior of a soft spring. This experiment has proved valuable as a project in a junior or senior physics laboratory. The results demonstrate the inadequacy of both the elementary formula for the period and the modified formula containing a correction term for the mass of the spring. A simple theoretical model is presented which yields results in agreement with experiment. The analysis uses mathematics that the students have been learning in parallel courses. The simplicity of the experiment serves to highlight the interplay of physics and mathematics. Most physics departments already have the elementary equipment needed.
The reflecting galvanometer as a damped, driven simple harmonic oscillator with recording facilities
Authors: Eagle B. A. , Jackson P. J.
Published: March 2005

The advantages of using a d’Arsonval galvanometer to demonstrate forced, damped simple harmonic motion in a laboratory course are greatly enhanced if the deflection of the galvanometer can be recorded as a function of time. This is easily accomplished by modulating the radial magnetic field in which the galvanometer coil moves at a frequency too high to produce a response in the galvanometer. A signal proportional to the angular deflection of the coil is then induced in the coil, and may be amplified, rectified, and recorded. A few sample results obtained in this way are given.
Demonstration holograph for comparing an image lens and a real lens
Authors: Rugheimer Mac , Kirkpatrick Larry D.
Published: March 2005

By making a holograph of a holograph, one can produce a picture in which the virtual image of a lens appears in front of a photographic plate while the images of various objects appear in or behind the plate. This virtual image of the lens has all the properties of an acutal lens when viewing these objects. It will even act as a real thin lens in combination with other real lenses.
The dark night sky paradox
Authors: Harrison E. R.
Published: March 2005

The infinite universe, uniformly populated with stars, was popularized in the 16th century. Early in the 17th century Kepler argued that within such a universe the sky everywhere would be as bright as the Sun. Since that time astronomers have sought in various ways to resolve the ’’dark night sky paradox’’ that is nowadays widely known as ’’Olbers’ paradox.’’ It is shown that the paradox has a simple resolution which has nothing to do with absorption of starlight, clustering of stars into galaxies, or expansion of the universe. The resolution is that stars do not shine long enough to fill space with sufficient radiation to create the bright sky visualized by Kepler.
Better instruction with lower costs: Some practical suggestions
Authors: Larkin Jill H. , Reif F.
Published: March 2005

We discuss some general guidelines and practical suggestions for systematically allocating limited resources so as to improve instruction, lower its costs, or both. Our main guideline consists of separating goals and assigning to each those resources which serve it best. We apply this procedure to selecting instructional goals, to dividing labor between human instructors and instructional materials (e.g., printed booklets, audio tapes), and to assessing student achievement. Our own experience with both PSI and conventional physics courses provides illustrations for these comments, which are generally applicable to both innovative and traditional course formats.
A European science study tour
Authors: Aman R. Wesley
Published: March 2005

A description of a science study tour that included visits to eight European cities is given. Visits to science museums, research centers, and educational institutions are listed, as are special lectures.
Electrical analogs of atomic radiative decay processes
Authors: Fontana Peter R. , Srivastava Rajendra P.
Published: March 2005

Simple electrical circuits are analyzed, and the results show that for high frequencies they have frequency and time responses identical to the spontaneous radiative decays of atoms. As an illustration of the analogy a two-circuit electrical system is compared with a two-level atom. The comparison leads to the identification of electrical analogs for quantum-mechanical quantities. It is also shown that the responses of an appropriate electrical circuit can be compared with the decay characteristics of coupled three-level atomic systems.
Fresnel diffraction of slow neutrons
Authors: Klein A. G. , Martin L. J. , Opat G. I.
Published: March 2005

Fresnel diffraction patterns were observed with a beam of slow neutrons of wavelength 4.33 Å. Lateral coherence was obtained by passing the beam through defining slits of 5.0-μm width. The required spatial resolution in the plane of detection was achieved by employing the track-etch technique in a film of cellulose nitrate held against a 10B target.
Temperature, transitivity, and the zeroth law
Authors: Bergthorsson Bjo/rn
Published: March 2005

Different statements of the zeroth law are examined. Two types of statements—which characterize two aspects of temperature—are found. A new formulation of the zeroth law is given and a corollary is stated. By means of this corollary it is shown how temperature and transitivity are used to disclose new nonthermal modes of interaction.
Primer of digital CMOS electronics
Authors: Trimmer William Stuart Newberry
Published: March 2005

Recently, CMOS logic has become attractive for use in the laboratory and introductory electronics courses. The ease with which it can be used, the high noise immunity, the ability to be easily modified to make oscillators, Schmidt triggers, etc., and the recent drop in price make this logic worthwhile learning. This paper will discuss input and output characteristics, some basic circuits, and how to interface CMOS to other devices.
Unexpected rewards
Authors: Hoffmann Banesh
Published: March 2005

E d i t o r’s Note: The substance of this article was delivered at the dedication of the Schenectady Archives of Science and Technology, Schaffer Library, Union College, in Schenectady, New York, in 1976. It presents, for both students and teachers of physics, a picture of the kind of atmosphere in which discoveries are really made and the sophistication with which one must search the archives in order to reconstruct this atmosphere. The original version was published by arrangement with the Friends of the Union College Library, and copies of it may be obtained, on request, from the Schaffer Library, Union College, Schenectady, NY 12308.
Rutherford revisited: Deflection of an electron in inverse first-, second-, and third-power central fields
Authors: Hubbell Harry H. , Birkhoff Robert D. , Allen UF John D.
Published: March 2005

The classical scattering equation for a charged particle moving in a plane perpendicular to the axis of inverse first- (cylindrical), second- (spherical), and third-power central fields has been solved by a general computer program for the experimental case of a bounded field. The particle enters with a known energy and impact parameter through a hole in a grounded electrode having a large but finite radius, and exits at the same radius after passing by a very small central electrode having a given potential. Results were computed and plots are given for the distances of closest approach of the particle to the scattering center, and the exit angles for the three cases for a large range of impact parameters and ratios of applied potential to initial energy. Our computer results for the spherical field check analytic solutions for Rutherford α particle scattering.