bluuebunny/crossref_metadata_2025 huggingface dataset:
Sound Wave Propagation in a Moving Medium and the Michelson-Morley Experiment
Authors: Morack J. L. , Roberts T. D.
Published: August 2005

Two ultrasonic transducers mounted a fixed distance apart on air track carts are used to demonstrate the effect of relative motion of propagation medium on the transit time for a signal traveling in one direction over a constant distance, this effect being of first order in v/c. The experiment can be used to clarify the origin of the second-order term v2/c2, which arises from analysis of the Michelson-Morley experiment. Sample experimental data are presented.
On the External Magnetic Field of a Closed-Loop Core
Authors: Page Chester H.
Published: August 2005

An infinite solenoid, or a toroidal coil, has no external magnetic field for dc excitation but has a nonvanishing vector potential field. The development of the steady-state condition from the transient response to step excitation is discussed. Under ac excitation, an external magnetic field must be present, but in practical cases its magnitude is negligible.
Phase Diagrams for the Overdamped Oscillator
Authors: Jeffers William A.
Published: August 2005

Phase paths are constructed for the overdamped oscillator. It is shown that two of the phase paths are straight lines, one dividing cases for which the oscillator will overshoot the equilibrium position from the cases for which it will not, and the other straight line phase path being the asymptote which all phase paths except the first-mentioned linear path approach as t→∞. The case of critical damping is discussed as a limiting case.
Wave Packet Dynamics on Two-Dimensional Quadratic Potential Surfaces
Authors: Askar A. , Weiner J. H.
Published: August 2005

Computer-generated figures within the framework of the hydrodynamic analogy to the time-dependent Schrödinger equation are presented for the motion of Gaussian wave packets on two-dimensional potential surfaces. The three cases treated illustrate (a) motion in a potential well, (b) tunneling through a saddle point, and (c) scattering by a potential barrier.
Solution to Potential Problems near a Conducting Semi-Infinite Sheet or Conducting Disk
Authors: Davis L. C. , Reitz J. R.
Published: August 2005

An image technique (due to Sommerfeld) that is appropriate for finding the potential of an electrical charge near a conducting semi-infinite sheet is reviewed. The technique is extended to a conducting disk by a coordinate transformation. The forces on a charge near a conducting semi-infinite sheet and near a conducting disk are found. In this case, the potential is required to vanish on the surface of the conductors. By requiring the normal derivative to vanish, the forces on a magnetic monopole are computed for the same geometries. The application of Sommerfeld's Green's functions to certain boundary value problems is discussed.
Some Uncommon Thermodynamic Potentials and the “Thermodynamic Equations of State”
Authors: Gordon Roger P.
Published: August 2005

We show that a great many thermodynamic “potentials” may be constructed by applying the Legendre transformation to mixed-representation fundamental equations. We observe that many thermodynamic relations believed to be of special significance may be obtained simply as Maxwell equations from these various potentials.
A Profile of the Two-Year College Physics Teacher
Authors: Byrd J. W. , Adler C. G.
Published: August 2005

The results of a survey of 2-yr college physics teachers based on national and regional samples is discussed. Data are presented concerning teaching experience, the amount of undergraduate and graduate training, and areas in physics in which current training is adequate and in which more training is needed. Information is also included on their preference for the appropriate terminal degree, the desired level of additional course training, and the desirability of summer research opportunities.
College Physics Teacher Preparation—How to Do It?
Authors: Strassenburg A. A.
Published: August 2005

During the fall of 1970, the Department of Physics at the State University of New York at Stony Brook debated the wisdom of establishing a Doctor of Arts degree to prepare teachers for the 2-yr colleges. Some faculty members questioned whether recipients of this degree would compete favorably in today's job market with conventionally trained PhD and MS recipients. A survey of the chairmen of physics departments in the publicly supported 2-yr colleges in New York was conducted to answer this question. The results of the survey are presented.
The Response to Crisis—A Contemporary Case Study
Authors: Swetman T. P.
Published: August 2005

The initial response of the scientific community to a recent crisis situation is documented. The example chosen is the 1964 discovery of the two-body decay of the K20 meson: The more immediate reactions to this discovery, and to its implications for time reversal symmetry, are considered.
Deflection of Projectiles due to Rotation of the Earth
Authors: Burns G. Preston
Published: August 2005

It is stated frequently in elementary astronomy textbooks that rockets or shells fired northward or southward are deflected to the right in the northern hemisphere and to the left in the southern hemisphere due to the rotation of the Earth. Range tables for some projectiles show a reversal of the Coriolis deflection from right to left in both hemispheres for certain azimuth and elevation angles. An analysis of the effect of the Coriolis acceleration on the flight of projectiles fired from the surface of the Earth shows the opposing effects of horizontal and vertical velocities and yields the condition for zero deflection perpendicular to the line of fire and for deflection to the right or left.
Physics and Everything: A Bibliography
Authors: Bailey John M.
Published: August 2005

A bibliography is presented that lists references connecting physics or technology with other academic disciplines. It has been used with great success by students writing research papers as part of a general physics course for nonscience majors.
Experiences with a Free Undergraduate Laboratory
Authors: Beun J. A.
Published: August 2005

The objectives and methods of a free undergraduate laboratory are set forth. The main features are a close connection between the students and the research groups, a large amount of student freedom and responsibility, and no grading of the students. Inquiries show that students and staff members are very enthusiastic and that both are involved to a surprisingly high degree. The main objections against free laboratories prove not to apply here: Staff members spend only a very moderate amount of time in coaching experiments and costs of student laboratory equipment are reduced by the use of equipment belonging to the research groups.
Conservation Laws for Undergraduates
Authors: Plybon Benjamin F.
Published: August 2005

Conservation laws for physical systems are produced as first integrals for systems of differential equations by an elementary method which is systematic and accessible to undergraduates. It is shown that all first integrals for the system ẋk(t) = fk(x1, ċċċ, xn, t) (k = 1, ċċċ, n) are solutions of a linear first-order partial differential equation. Hence, they can be found by well-known textbook methods. This method is applied to some mechanical problems. A new first integral for projectile motion is derived and discussed.
A Survey of Opportunities Open to the Physics Major for Graduate Study in Other Fields
Authors: Lee R. S.
Published: August 2005

Sharply reduced employment opportunities may soon be reflected in a corresponding decrease in the number of students entering physics at the undergraduate level. Physics departments can responsibly seek to reverse this decline only if adequate opportunity awaits the physics major upon graduation. A survey has been conducted to gather information regarding opportunities open to the physics major who wishes to pursue graduate study in another field. The survey was conducted by means of a questionnaire. Questionnaires were sent to 317 department heads in 11 different academic fields. The survey included departments at 78 universities. The results of the survey support the conclusion that graduate study in another field is an attractive alternative that should be considered by physics undergraduates. A sufficiently flexible undergraduate physics program could be very attractive to an undergraduate with an interest in physics who wishes to pursue graduate study in some other field. Persons with an undergraduate physics degree and a graduate degree in some other field are in an advantageous position to contribute to multidisciplinary solutions of many of the current social, economic, and environmental problems.
The Discovery of the Beta Particle
Authors: Malley Marjorie
Published: August 2005

Natural radioactivity was discovered by Henri Becquerel early in 1896. Only after three and a half years had passed was it determined that (at least) part of this radiation consisted of material particles. Towards the end of 1899 three different sets of investigators in as many countries found independently that radium rays were bent when they traversed a magnetic field. This paper delineates both the reasons for this delay and the events which converged in 1899 to make likely the simultaneous discovery of the deflection of the beta rays in a magnetic field. It also indicates the significance this discovery had for the future development of radioactivity.
Lorentz Transformations in the Presence of a Uniform Gravitational Field
Authors: Broucke R.
Published: August 2005

This article describes a Lorentz-like transformation between a fixed frame and an inertial frame that is free falling due to the presence of a uniform gravitation field. The application to the clock paradox problem and some connections with similar works are also discussed.
Mathematical Formulation of the Interference Laws of Fresnel and Arago
Authors: Collett Edward
Published: August 2005

The mathematical representation of each of the four interference laws of Fresnel and Arago is presented. Each of the laws is characterized by a unique Stokes vector. These vectors are arrived at by a matrix analysis of the, interference experiments of Fresnel and Arago in which only polarizers are used. The historical motivation that led Stokes to introduce the parameters that now bear his name is noted. The similarity in the approach taken by Stokes to represent the fundamental properties of the classical optical field in terms of observables is compared with Heisenberg's approach to the formulation of quantum mechanics. The mathematical statements that characterize unpolarized light are developed. These statements are then used to determine the Stokes vectors that describe each of the four interference laws of Fresnel and Arago. In a final section of the paper the mathematical apparatus developed here is used to describe Young's interference experiment with unpolarized light.
DITRAN: A Program for Translating Physics Dialogs into Templated Conversational CAI Programs
Authors: Bauer J. , Magerlein J. , Sherman N.
Published: August 2005

We describe here the structure of a set of computer programs (DITRAN) that translate the text of conversational exchanges appropriate for elementary physics discussions into an operational computer-based dialog. Dialogs produced in this manner are designed as a series of templated subprograms. The structure of a simple template is reviewed. Detailed instructions on the use of DITRAN and a few illustrative examples can be obtained on request. Arrangements may be made to access DITRAN for experiment and development of instructional dialogs.
Students' Calculation of Cosmic Ray Trajectories
Authors: French John D. , Lamb William H. , Young Philip J.
Published: August 2005

The use of the computer to integrate a system of ordinary differential equations has been incorporated into a course for advanced students. The pedagogical value of the problem chosen, which is Størmer's method for numerical integration of the equation of motion for a charged particle in a dipole magnetic field, is discussed. It is pointed out that a procedure developed by Størmer in 1936 for finding individual cosmic ray trajectories forms an adequate substitute for a table of trajectories for the dipole approximation to the Earth's magnetic field if one programs Størmer's numerical procedure for an electronic computer. Trajectories of primary cosmic ray particles incident on the top of the atmosphere at 41° north geomagnetic latitude have been calculated by numerical integration for a variety of energies and directions at the point of impact. The mathematical problem is reviewed, the results are presented as graphs of representative trajectories, and a table of asymptotic directions is given for those trajectories.
Apparatus Drawings Project. Report Number 17. Small X-Ray Tube
Authors: Marcley Robert G.
Published: August 2005

A small well-shielded high-vacuum molybdenum-anode x-ray tube designed for use as an ionizing source with a Millikan oil-drop apparatus is described. An accelerating potential of 28-kv peak provides a continuous x-ray spectrum with a short-wavelength cutoff of 0.436 A as well as the intense K, L, M, and N series of the characteristic line spectrum of molybdenum. The 28-kv accelerating potential, with a saturation current of 0.2–0.3 ma rms, ensures adequate ionization with conventional equipment, while still permitting the convenient installation of the massive external shielding necessary in a teaching laboratory. Information on essential safety precautions and construction procedures is given.
Applications of Superconductivity
Authors: Goodkind John M.
Published: August 2005

A general review of current practical applications of the properties of superconductors is presented. The devices are classified into groups according to the property of superconductors which is of primary importance to the device. A brief introduction to each of these properties is given and extensive references to the literature are supplied so as to make it possible for a novice in the field to grasp the technical implications of superconductivity. (This is another in the series of review-tutorial papers that are written at the invitation of the Editor and that will be published from time to time in the American Journal of Physics. Articles in this series will be of an expository, critical nature and are intended to be eminently readable by students and professionals alike as a first introduction to a specialized topic.)
James Franck at Göttingen
Authors: Oldenberg O.
Published: August 2005

These recollections were written at the request of the Project on the History of Recent Physics of the American Institute of Physics.
Harmonic Oscillator with Cylindrical and Spherical Symmetry
Authors: Carlstone D. S.
Published: August 2005

The cylindrically and the spherically symmetric harmonic oscillators are considered by means of matrix techniques in a basis that is appropriate for each symmetry. For example, the spherically symmetric oscillator is described by the radial and angular momentum quantum numbers. The energy eigenvalues and the matrix elements of the promotion-demotion operators are found in each case. By expressing the operators in curvilinear coordinates, the promotion-demotion operators are used to deduce the form of the corresponding wave functions.
An Instructive Example of the Bootstrap Hypothesis
Authors: Abbe W. J.
Published: August 2005

A simple example is constructed which illustrates the bootstrap concept in classical mechanics, and may be useful in communicating the idea to undergraduates and/or advanced high school students.
Relativistic Calculations of Angular Distributions and Correlations in a Three-Body Phase Space with Constraint Functions
Authors: Proriol J. , Laverriere R.
Published: August 2005

We derive a method for computation of angular distributions and angular correlations in a three-body phase space. Earlier papers did not take account of a constraint function connected with the dynamics of the problem. With the relations given in this paper we can easily compute the integrals giving the angular distribution and correlation. Some applications are presented.
A Simple Picture for Dirac's Charge-Pole Quantization Law
Authors: Lubkin Elihu
Published: August 2005

If something appears to bear a magnetic monopole of strength g not equal to a multiple of (2e)−1, as a result of measurement of the magnetic field about it over most of the 4π solid angle, then at least one visible bar magnet will be found by the electron-optical interferometric experiment of Aharonov and Bohm, in the remaining solid angle.
Light λ0 Hypernuclei and the Lambda-Nucleon Potential
Authors: Porter L. B.
Published: August 2005

Characteristics of light hypernuclei are described. Exploitations of hypernuclei in studies of the lambda-nucleon force are reviewed, with emphasis on phenomenological potential well parameters. Results of studies of lambda-nucleon scattering and final state interactions are summarized. Properties of the lambda-nucleon force are discussed briefly.
Determination of Energy Levels in Stable Nuclei by Neutron Inelastic Scattering
Authors: French W. R. , Wehrbein W. M. , Goss D. , Gasper J. K.
Published: August 2005

Neutron inelastic scattering experiments are conceptually simple yet instructive. The energy levels of some stable nuclei were determined by measuring the energies of the gamma radiation produced by the (n, n′γ) reaction with the target nuclei. The source of neutrons was a Pu-Be source. The gamma spectra were obtained with a Ge(Li) detector and a 4096 channel analyzer. A computer program was used to determine the channel locations of the gammas and to calculate their energies. Besides the measurement of energy levels of the detector material (Ge), levels have been measured in Fe, Al, Mg, Pb, Na, Cl, Zn, and Cu.
Absorption Coefficients for Plane Ripples on Deep Fluids
Authors: Walbridge N. L.
Published: August 2005

A constantly operating, long, straight wave maker in a ripple tank produces waves whose amplitude decreases exponentially with the distance x from the wave maker. The coefficient of x is the spatial coefficient of absorption. The relation between this coefficient and the kinematic coefficient of viscosity is derived directly for the case of a clean surface and a deep fluid. Some familiarity with Lamb's Hydrodynamics is necessary for the reading of the article.
A Spin Flip Problem
Authors: Robiscoe R. T.
Published: August 2005

We examine the problem of calculating the spin up and spin down amplitudes for a spin 12 particle, initially aligned with respect to a constant magnetic field, and then subjected to a rotation of the field through an arbitrary angle in a finite time. We find that the solutions to the problem are entirely determined by an adiabaticity parameter α which is the ratio of the particle Larmor frequency to the field rotation rate. As expected, a spin flip occurs readily only in the nonadiabatic case, α≪1.
Variational Calculation with Harmonic-Oscillator Eigenfunctions
Authors: Aguilera-Navarro V. C. , Méndez V. R. M.
Published: August 2005

Variational calculations play an important role in quantum mechanics, particularly in determining the ground-state energy of physical systems. Didactic examples in which one can see how the exact energy and wave function are approached by using a family of trial functions are not very numerous. An example was given in a recent book [M. Moshinsky, The Harmonic Oscillator in Modern Physics: From Atoms to Quarks (Gordon and Breach, New York, 1969)] which discusses the ground state of the hydrogen atom using as trial wave function a linear combination of harmonic-oscillator states. In the present paper we carry out a similar analysis for the ground state of a particle of mass m in a three-dimensional square-well potential. We discuss not only the approach to the exact energy when we vary the frequency and the number of oscillator states but also analyze the overlap of the exact and variational wave functions and compare the exact and approximate form factors.
Force on a Magnetic Dipole
Authors: Greene Jack B. , Karioris Frank G.
Published: August 2005

In this paper we derive the expression for force on a magnetic dipole in an elementary way but without using “poles.” The equation F = (μ ·∇)B follows from concepts of electromagnetism already familiar to the first-year student. This is accomplished by working with forces on current elements and grouping terms to attain recognizable vector identities. In a similar manner, it is shown that the potential energy is U = −(μ·B). Introductory physics texts generally do not discuss force on dipoles. More advanced texts treat the problem by analogy to the electric dipole or by pure mathematical formalism which is beyond the level of the beginning physics major.
Analysis of Strobe Photographs Using a Desk-Top Computer
Authors: Powell Harry D. , Whitson John C. , Miller James R.
Published: August 2005

Two experiments are described in which a desk-top computer has been used in the introductory physics laboratory as an aid in the analysis of strobe photographs. Applications to the collision of two pucks on an air table and to the motion of a ball on a stretched rubber band are presented to illustrate that the desk-top computer can eliminate many of the mechanical aspects of data handling required in strobe photograph analysis, allowing the student to concentrate on the physical significance of the problem. The effectiveness of the desk-top computer in large laboratory classes and in classroom demonstrations is discussed.
Boundary Conditions for Moving Magnetic Fields and Lorentz Transformation of Surface Currents
Authors: Noerdlinger Peter D.
Published: August 2005

The usual boundary condition relating tangential magnetic field discontinuity to surface current requires modification when the boundary is moving. Surface currents suffer a Lorentz reduction (1−β2)1/2 when observed in a reference frame moving at speed βc normal to their flow.
The Brehme Diagram in Two Spatial Dimensions
Authors: Albergotti J. C. , Larkin J. H.
Published: August 2005

An extension of the Brehme diagram is given which describes two spatial dimensions and one time dimension. The extended diagram is applied to several problems in special relativity: the Lorentz velocity transformations, the transverse Doppler effect, the Michelson-Morley experiment, the transformation of the direction of propagation of light, and the visual appearance of rapidly moving objects.
Green's Function Treatment of Two-Spin Heisenberg Ferromagnet
Authors: Kuiper L. K. , Adels Jeffrey J.
Published: August 2005

The Green's function method is applied to a system consisting of a two-spin Heisenberg ferromagnet in a magnetic field. Using a decoupling procedure devised by Roth with both commutators and anticommutators of the spin operators in both the Both procedure and in the Green's function formulas, it is possible to obtain more than one solution for the magnetization and the correlation functions. The various solutions are compared with a solution produced by using a Tyablikov decoupling and also with the exact solution, which can be obtained because of the simplicity of the system.
Energy and Momentum in Electromagnetic Field for Charged Particles Moving with Constant Velocities
Authors: Boyer Timothy H.
Published: August 2005

The relationship between the Lorentz force and the energy and momentum in the electromagnetic field is illustrated with some striking examples for systems of point charges moving at constant velocities. For these systems, the kinetic energy and momentum associated with particle mass do not change, while the external forces which balance the interparticle Lorentz forces give exactly the rate of change of energy, momentum, and angular momentum in the electromagnetic fields. Calculations along roughly these lines have been performed to order c−2 by Page and Adams. The present evaluations are noteworthy in that they are exact, and also in that the necessary electromagnetic field integrals over all space have been reduced to delta function integrations. In the limiting charge distributions involving infinite energy density at spatial infinity, the connection of the Lorentz force with electromagnetic energy and momentum is lost.
Derivation of the Davydov Distribution from the Boltzmann Equation
Authors: Wannier Gregory H.
Published: August 2005

The Davydov distribution is the distribution of speeds of a dilute electron gas in the presence of an electric field and a dense gas of neutral molecules, whose thermal motion is not negligible or even small. The present derivation proceeds directly from the Boltzmann transport equation. Previous derivations proceeded from other equations or postulated certain coefficients from outside information.
Experiment for Studying the Magnetization of Superconductors
Authors: Vaughan M. , Ragona A. , Marcuso M. , Joiner W. C. H.
Published: August 2005

An advanced laboratory experiment is described for determining superconducting magnetization curves. The experiment uses an integrating circuit which results in rapid acquisition and reduction of data and permits experiments of some latitude. The student is able to make a choice of the features he wishes to study. Student data are presented.
On the Repulsion of Slow Neutrons by Attractive Potentials
Authors: Peshkin M. , Ringo G. R.
Published: August 2005

A naive calculation of the scattering of slow neutrons by an attractive square-well potential gives a distribution of scattering amplitudes that agrees rather well with available measured amplitudes for thermal neutrons.
Holographic Determination of Simple Translation and Rotations
Authors: Floyd R. P. , Collins D. J.
Published: August 2005

Two simple holographic experiments are described which have been found useful in the development of an understanding of the application of holography to interferometric measurements of displacements and rotations. These experiments have been used as part of an instructional laboratory in optical methods in gas dynamics. As part of this laboratory, interferograms have been taken and rotations and displacements determined from the interferogram.
Experiences of University Physicists Working with their Two-Year College Neighbors
Authors: Strassenburg A. A.
Published: August 2005

The growth of the 2-year college movement has been rapid, probably because these institutions offer a wide variety of programs relevant to the needs of our technological society for highly trained workers in many different professional fields and career areas. Because 2-yr colleges are breaking new ground, they are encountering problems: (1) difficulties in articulating with degree-granting institutions; (2) students who are weaker academically and lower socioeconomically than typical 4-yr college students; (3) a shortage of suitable teaching materials; and (4) inadequate supplies of appropriately prepared teachers. Programs supported by the Esso Education Foundation and the National Science Foundation at the State University of New York at Stony Brook have been designed to minimize these problems for the physics departments of the New York 2-yr colleges.
Solutions of Static Field Problems with Periodic Sources
Authors: North Gerald R.
Published: August 2005

A method due to Poisson is used to solve a class of problems in classical static field theory. When the field may be written as an infinite sum of contributions due to an array of identical sources, the field may be Fourier analyzed explicitly and its form analytically extended to all space. As an example a detailed calculation is presented for a sequence of current loops.
State Function Formulation of Elementary Relaxation Processes
Authors: Phillipson Paul E.
Published: August 2005

The approach to thermal equilibrium of a free particle and a harmonic oscillator interacting with a heat bath can be understood from a semiclassical point of view in terms of the time evolution of a quantum mechanical state function appropriate to each system. The state functions are parameterized such that expectation values comply with the predictions of the classical theory of Brownian motion, with the consequence that the Fokker-Planck equation for a free particle in velocity space, the Montroll-Shuler equation for a quantum oscillator in discrete energy space, and their solutions are arrived at by a common procedure. These relaxation processes become visualizable as the progressive development from a coherent, relatively ordered state to that of equilibrium, so that the loss of information as equilibrium is reached and the consequences of random phasing can be traced dynamically in some detail. The unity of approach is reinforced by the demonstration that since both equations represent Markoffian processes, the Montroll-Shuler equation predicts distributions in coordinate space and momentum space which satisfy a Fokker-Planck equation.
Change of Phase on Reflection
Authors: Sandhu H. S. , Friedmann G. B.
Published: August 2005

Orientation of the azimuth of a beam reflected from an isotropic dielectric medium is discussed with respect to the azimuth of a plane polarised incident beam. The choice of handedness of the reflected coordinate system should be stated, and it is pointed out that numerical results must always be referred to an appropriate vector diagram if ambiguity is to be avoided.
Inexpensive Applications of Holography
Authors: Taylor C. E.
Published: August 2005

An inexpensive holography system is described which can be used to show many of the capabilities of holography in science and in art. Applications such as time-lapse interferometry, time-averaged interferometry, holographic microscopy, and real projected image holography are discussed. The last is often of great interest to students involved in photography and art.
A Development of the WKB Approximation by Use of Transformations
Authors: Engelke Ray
Published: August 2005

The WKB wavefunctions for one-dimensional nonrelativistic problems are derived by a simple transformation method. By applying the Liouville substitution to Schrödinger's equation and then neglecting certain “small” terms in the transformed equation, one arrives at the WKB solutions. The terms neglected in obtaining the WKB solutions are explicit. No asymptotic expansions are used in the derivation. Use of a known criterion from the theory of differential equations gives assurance that the WKB solutions are asymptotic to exact solutions of Schrödinger's equation in certain cases.
Optical Homodyning, Theory and Experiments
Authors: Gilheany John J.
Published: August 2005

Phase modulation of the light in one leg of a Michelson interferometer, optical homodyning, is explained in terms of the physical motion of the interference fringes. The theory for visual and electro-optical observation of the fringes is presented. The experimental equipment is described and several experiments are suggested at the advanced undergraduate level.
Linear Momentum of the Source of a Static Electromagnetic Field
Authors: Calkin M. G.
Published: August 2005

It is shown that in general a stationary system of charges and currents generating a static electromagnetic field has net linear momentum. Explicit expressions for this momentum are found, and the physical origin of the momentum is brought out by means of examples.
Mean Free Paths, Ion Drift Velocities, and the Poisson Distribution
Authors: Varney Robert N.
Published: August 2005

In elementary kinetic theory of gases, the topic of free paths is usually limited to the simplest case of finding the probability of zero collisions in a travel distance x. This leads to a mean free path and it also discloses that the greatest probability of collision in a distance Δx occurs for x = 0. The most probable free path then does not coincide with the mean free path. This paper carries on the analysis to evaluation of the probability of exactly one collision in a distance x and still further to the probability of exactly n collisions in x. All of these probabilities, for which the number of collisions n is greater than zero, are bell-shaped curves with the most probable value of x coinciding with n times the mean free path. The results are applied to analyze the sharpness of the observed drift velocity of ions moving through a gas in an electric field.
Waves in Dispersive Media: Another Use of Computers in Introductory Physics
Authors: Merrill John R.
Published: August 2005

This note presents a simple, intuitive approach to the propagation of waves in dispersive media. The method analyzes a wave pulse into Fourier components, propagates each component according to its wave-vector dependent phase velocity, and then resynthesizes the wave train. The method uses a computer to perform the algebra; a program which minimizes central processor time while maximizing the intuitive content of the calculation is given in the appendix.
Laboratory Experiments Involving the Two-Mode Analysis of Coupled Oscillators
Authors: Blair J. Morris
Published: August 2005

Three examples of simple coupled oscillators are presented that allow easy adjustment of the amount of coupling between the oscillators. This makes convenient the observation of beats of variable duration which should aid a student's understanding of the two-mode approach to the analysis of these systems. A table of factors is given which simplifies the calculation of the mutual inductance of equal, coaxial, flat coils.
Culvert Whistlers
Authors: Crawford Frank S.
Published: August 2005

I describe easily observable phenomena that are the acoustical analog of electromagnetic whistlers that occur in the earth's atmosphere. Then I give a simple derivation of the dispersive behavior of waves in a wave guide, and compare sound modes and electromagnetic modes in cylindrical wave guides.
Derivation of a Hamiltonian for a Charged Particle without Recourse to Electromagnetic Potentials
Authors: Hansen Aage E.
Published: August 2005

The Hamiltonian for a charged particle in an electromagnetic field is usually presented in terms of the electromagnetic potentials A and φ. However for discussions of a large number of atomic and molecular properties, it is more convenient to have available a Hamiltonian which is expressed directly in terms of the more familiar electric field E and magnetic induction B. Here it is shown that one can construct a generalized velocity-dependent potential function of E and B, which yields the correct expression for the Lorentz force (truncated after the electric quadrupole, magnetic dipole terms). From this generalized potential the corresponding classical Lagrangian and Hamiltonian are obtained directly in terms of E and B. The transition to a quantum mechanical [E, B]-dependent Hamiltonian operator is considered, and we list a variety of, static as well as time-dependent, atomic and molecular properties which can be discussed in a unified way using this Hamiltonian as a starting point.
Velocity Amplification in Collision Experiments Involving Superballs
Authors: Harter William G.
Published: August 2005

If a pen is stuck in a hard rubber ball and dropped from a certain height, the pen may bounce to several times that height. The results of two such experiments, which can easily be duplicated in any undergraduate physics laboratory, are plotted for a range of mass ratios. A simple theoretical discussion which provides a qualitative understanding of the phenomenon is presented. A more complicated formulation which agrees very well with one of the experiments is also presented. The latter involves a simple analog computer program. Finally, an intriguing generalization of the phenomenon is considered.
The Faraday Effect and Inversion Symmetries
Authors: Rinard Phillip M. , Calvert James W.
Published: August 2005

The usual explanation of the Faraday effect uses an artificial model of matter and does not achieve complete success. By approaching the effect from a less microscopic viewpoint, it is shown that the effect is consistent with the space- and time-inversion symmetry laws. The effect of the charge inversion is also discussed. While not explaining the Faraday effect, the predictive ability of the symmetry laws is demonstrated, and the assignments of electric and magnetic fields after symmetry operations is discussed.
The Effect of Air Resistance on Falling Balls
Authors: Lindemuth Jeffrey
Published: August 2005

An experiment suitable for use in undergraduate physics courses is described to measure the effect of air resistance on falling balls. The results are in good agreement with those predicted by a theory with a resistive force depending on the square of the velocity.
Binocular Observation of Moving Objects
Authors: Boas Mary L. , Calhoun Richard C. , Horan Owen
Published: August 2005

In recent years a number of papers have considered the appearance of objects moving at relativistic speeds as seen by a single observer. This paper explores the stereoscopic effects of using a pair of eyes or observing instruments, assuming that the light rays from the object arrive simultaneously at the two eyes and that the instantaneous apparent position of a point object is the intersection of the lines of sight of the two eyes. Contrary to what is true for objects at rest, stereoscopic observation of moving objects does not determine correctly either their shape or position.
Dynamical Applications of Bargmann Space I. Pure Bose Systems
Authors: Robinson J. M. , Trubatch S. L.
Published: August 2005

Practical aspects of the Bargmann space representation of quantum mechanics are detailed. Models which are quantized by imposing the entirety and growth-rate conditions are analyzed. The extension of coherent state space techniques to multimode systems is accomplished, and some illustrative models are solved.
Dynamical Applications of Bargmann Space II. Interacting Bose-Fermi Systems
Authors: Robinson J. M. , Trubatch S. L.
Published: August 2005

Bargmann space techniques are extended to interacting Bose-Fermi systems. The one-mode Fried model is used as an illustrative example. Comparison is made with the eigenfunctions and eigenvalues obtained by direct diagonalization.
Perpetual Motion of the Zeroth Kind
Authors: Wangsness Roald K.
Published: August 2005

We investigate the characteristics of a perpetual motion machine whose operation depends on a violation of the zeroth law of thermodynamics. It is found that it operates by creating work, but is necessarily a composite of at least two systems in contrast to a machine of the first kind.
A Microwave Analog of Optical Rotation in Cholesteric Liquid Crystals
Authors: Gerritsen Hendrik J. , Yamaguchi Richard T.
Published: August 2005

A microwave structure was built that is, essentially a scaled up model of a cholesteric liquid crystal. The model consists of a series of thin plastic sheets to which copper wires are attached of dimensions small compared to the microwave length. The direction of the wires on successive sheets varies in a screw-type fashion while the distance between successive sheets and thus the pitch of the screw can be varied. This model shows optical rotation and also, when the period of the screw structure is approximately equal to the wavelength of the microwaves used, the behavior typical of cholesteric crystals, that is, one sense of circular polarization is reflected, the opposite sense is transmitted. Qualitative agreement with experiments in light reflection and transmission using a cholesteric liquid crystal was obtained.
On Boundary Conditions for an Infinite Square-Well Potential in Quantum Mechanics
Authors: Seki Ryoichi
Published: August 2005

A well-known problem of an infinite square-well potential in quantum mechanics furnishes an interesting boundary condition. We investigate this in detail by considering the infinite square-well potential as a limiting case of an finite square-well potential.
Relationship between Nonlocal and Velocity-Dependent Potentials
Authors: Kiang D.
Published: August 2005

The statement that a nonlocal potential is equivalent to a velocity-dependent potential is examined. Problems which arise from the expansion of a nonlocal potential into a finite power series in the momentum operator p are discussed.
Detectors and Linewidths in Mössbauer Spectroscopy
Authors: Schmidt Stanley A.
Published: August 2005

Some general considerations on the effects of detectors, sources, and absorbers on the widths of spectral lines observed in Mössbauer experiments are reviewed, with particular emphasis on qualitative understanding of the underlying principles. The derivation of the observed line shape is outlined for both conventional and resonant detectors, and the underlying reason for the resonant detector's improved resolution explained. The limiting results for the ideal case of Lorentzian source and absorber of negligible thickness are given, and the influence of finite source and absorber thickness discussed.
External Field of an Ideal Toroid
Authors: Page Chester H.
Published: August 2005

The external magnetic field of an ideal toroid vanishes for dc excitation but not for ac excitation. The external static field has a nonvanishing vector potential; the emf in a transformer winding is due to the time variation of this vector potential. An expression for the external magnetic field is derived, and it is shown that the external flux density is a negligible fraction of the flux density in the core.
Are Colleges Concerned with Intellectual Development?
Authors: McKinnon Joe W. , Renner John W.
Published: August 2005

The assumption is often made by college professors that incoming freshman students think logically. Using tests designed by the Swiss psychologist Jean Piaget to evaluate logical thought processes, the authors found that 66 of 131 freshmen exhibited characteristics of the concrete operational thinker, while another 32 did not meet the criteria for formal operations. Professors further compound the problem by failing to recognize the kinds of experiences incoming freshmen students must have to move toward more logical thought. McKinnon, using a newly developed inquiry-oriented science course based upon Piagetian criteria, found a highly significant difference between those students who were exposed to the course and like students who were not. The authors concluded that secondary and elementary teachers do not take advantage of inquiry-oriented techniques so necessary to the development of logical thought because college professors do not provide examples of inquiry-oriented teaching.
Radiation Field of a Charge Moving on a Straight Line
Authors: Alevisos J. O.
Published: August 2005

A derivation of the radiation field of a charge accelerating on a straight line is presented that makes use of Gauss' law in a direct manner and does not make use of the concept of lines of force.
Regge Poles and Bound States of Nonrelativistic Scattering Systems
Authors: Kronenfeld Richard
Published: August 2005

A heuristic argument which avoids using the Sommerfeld-Watson transform is presented for the existence of bound states for a potential at the poles of its partial-wave scattering amplitude in the physical sheet. We obtain a general formula for bound state Regge trajectories from the Jost function φ+(l, k2) and apply it to four potentials— Coulomb, harmonic oscillator, delta shell, and spherical well. The concluding section examines some properties of Regge trajectories in nonrelativistic scattering and the extension of Regge pole theory to relativistic particle interactions.
An Exactly Solvable Model Exhibiting a Landau Phase Transition
Authors: Alben Richard
Published: August 2005

An exactly solvable model is presented that exhibits a phase transition and that can be exactly described by Landau's phase transition theory. The model is used to elucidate the constructs and assumptions that go into the Landau theory, and also to illustrate the role of fluctuations near an instability in a finite system.
The Structure of the Multipole Treatment of Intermolecular Forces
Authors: Meath William J.
Published: August 2005

A simple pictorial device, the intermolecular force triangle Δv, is introduced, which is capable of representing the structure and the physical content of the theory of intermolecular forces. The structure of the multipole expansion of the interaction potential energy, the first-order interaction energies arising from the interaction of the permanent moments of the interacting species, and the second-order induction and dispersion energies are discussed. Specific interactions are also considered that illustrate the usefulness of the intermolecular force triangle in predicting the various types of interaction energies that can arise in a given atomic or molecular collision.
Charge-Carrier Equilibrium in Semiconductors According to the Mass-Action Law
Authors: Christy R. W.
Published: August 2005

The application of the thermodynamical law of mass action to the calculation of equilibrium conduction electron and hole concentrations in semiconductors is explained. The method can be applied to arbitrarily complicated systems of donors, traps, acceptors, etc., in addition to the intrinsic electron-hole excitation. The discussion is limited to small defect concentrations and quasifree charge carriers, so that the ideal-gas free energy and the Sackur-Tetrode entropy constant can be used. Exact solutions are straightforward but often so complicated that simplifying assumptions are useful. As an example the effect of compensation of donors is calculated as a function of temperature. The Fermi energy is simply related to the electron concentration.
Pictures of Dynamic Electric Fields
Authors: Tsien Roger Y.
Published: August 2005

The electric field of a point charge moving at relativistic velocities along a single plane of motion may be visualized in a physically intuitive way with the aid of pictures of the electric lines of force. A general derivation of exact parametric equations for these lines of force is described and applied to create the pictures presented here of synchrotron radiation, low-angle high-energy Coulomb scattering, abrupt linear acceleration of a charge, and a charge undergoing simple harmonic motion.
Introduction to the Thermodynamics of Biopolymer Growth
Authors: Kittel C.
Published: August 2005

An elementary discussion for physicists is given of the thermodynamic instability of proteins and DNA. The biochemical explanation is given of how these molecules are grown in the face of a large unfavorable free energy difference, as much as 0.2 MeV for DNA of 106 bonds. The role of ATP is described as the major fuel of the biological world.
Approximately Relativistic Interactions
Authors: Kennedy Frederick James
Published: August 2005

The well-known application of the Lorentz transformation to the exactly relativistic Coulomb force in order to derive the force on a charge due to another in uniform motion is extended to arbitrary Lorentz-invariant one-body problems. It is shown that the result, in addition to being the force on m1 from uniformly moving m2, is, to first order in coupling strength, the Lorentz-invariant force on m1 when m2 is unconstrained and the two particles interact. Some attention is paid to Lagrangians for exactly relativistic one-body problems, and a new construction of Darwin-like 1/c2 corrections to nonrelativistic Lagrangians for a variety of interactions is presented. Among these is the EIH Lagrangian of general relativity, whence follows an interesting point concerning special relativistic gravitation.
A Direct Method of Vector Differentiation in Orthogonal Curvilinear Coordinates
Authors: Yang H. T.
Published: August 2005

A direct method is presented for the vector differential operations in orthogonal curvilinear coordinates. From the angular displacement vector of the diagonal of the parallelepiped formed by the orthogonal coordinate line elements the variation of the unit vectors are obtained. Then the vector differential operations are directly carried out. In this way, expressions for gradient, divergence, curl, and Laplacian in cylindrical, spherical, and elliptic coordinates are derived.