bluuebunny/crossref_metadata_2025 huggingface dataset:
Inexpensive two-dimensional measuring device for cryogenic temperatures
Authors: Carles A. Grau
Published: August 2005

A simple device for measuring thermal deformations in two-dimensional samples cooled to liquid nitrogen temperatures is described. The measurement consists of adding liquid nitrogen to a transparent quartz tray, and then scanning the sample from the bottom with a flatbed scanner. As a test of the device, the thermal contraction of aluminum from room temperature to 77 K is measured. The application of Grüneisen’s approximation leads to good agreement between the calculated and tabulated contraction percentages.
Some Experiments on Nuclear Magnetic Resonance
Authors: Donnally Bailey L. , Bernal G Enrique
Published: August 2005

Nuclear magnetic resonance experiments are described which illustrate how spins in liquid and solid samples interact with their environment. A conceptually simple way of measuring the spin-lattice relaxation time is given, and demonstrations of uncertainty broadening, correlation time narrowing and the adiabatic theorem are discussed. Very simple apparatus is required for these experiments and demonstrations.
Geometrical Demonstration of Velocity Transformation in Special Relativity
Authors: Daubin Scott C.
Published: August 2005

The relativistic velocity transformation is demonstrated by a graphical representation of a “thought experiment” using a moving rod containing a moving element. In the frame in which the rod is at rest the moving element is observed to possess a certain velocity; the requirements of the theory are then applied to present graphically a series of events which determine the velocity of the moving element in the frame in which the rod is in motion.
Interference Pattern of Beats
Authors: Hoxton L. G.
Published: August 2005

Demonstration experiments are described and an elementary theory is given, both dealing with the well-known concept that the “beats” arising from two sources of slightly differing frequencies may be described in terms of a traveling pattern of interference fringes. A ripple tank and a special simple generator of ripples at two points were employed. Amplified audible beats from the generator would match the frequency of appearance of the fringes as seen in the tank or projected on a screen. The form of the fringes are closed curves known as Cartesian ovals. They are higher curves that degenerate into expanding circles when the two point sources coincide, or into stationary hyperbolas when their frequencies are equal.

The theory for these fringes, their spacings and velocities, is elementary in the sense that, with one exception (dispersive media), use of the calculus is a matter of taste, not of necessity. It is on the level of the college student.
Plasma Equation of State
Authors: Kelly Don C.
Published: August 2005

The equation of state for a plasma is derived from the virial theorem. The result is expressed in a form which shows that deviations from the ideal gas law are minor under conditions which validate use of the Debye-Hückel potential.
Coefficient of Thermal Expansion and Young's Modulus for a One-Dimensional Model of a Solid
Authors: Mazur J. , Rubin Robert J.
Published: August 2005

The classical statistical mechanical theory of one-dimensional systems of particles which interact only with their nearest neighbors is applied to a simple model of a solid. The relative distance between neighboring particles is limited to a finite range by the form of the assumed interaction potential. The virtue of the model is that simple exact expressions are obtained for the coefficient of thermal expansion and Young's modulus when the pressure on the system is zero.
Dynamical Theory of Atom Jumps in Crystals
Authors: Pearlstein Edgar
Published: August 2005

The jump frequency of a diffusing atom in a crystal is examined from a dynamical point of view. Its motion is considered to be the superposition of many independent sine waves—the lattice vibrations. Whenever a critical displacement is reached, the atom “diffuses.” The probability of the waves adding up to produce this critical displacement of the atom is calculated on the basis of an elementary model. Temperature is brought in by assuming equipartition of energy among the lattice vibrations. This work is a simplified version of the dynamical theory of Rice [Phys. Rev. 112, 804 (1958)], the simplifications being such as to reduce greatly the mathematical complexities in order to bring out better the physical process. No new results are claimed, but it is believed that this work has heuristic and pedagogical value.
Group Theoretical Consideration for the Intersection of Crystal-Ion Zeeman Terms
Authors: Marshall S. A. , Sperber D. , Fagen E. A.
Published: August 2005

An account is given of the manner in which terms transform when a time-independent magnetic field is applied to a crystal structure containing a magnetic ion. The terms in question are those of the magnetic crystal-ion. The discussion is based on the von Neumann-Wigner theorem concerning the nonintersection of terms having equivalent transformation properties. An example is given which illustrates this theorem.
Laboratory Experiments on the Hall Effect Using Evaporated Metal Films
Authors: Jeppesen M. A. , Flagg S. R. , Rancourt J. D.
Published: August 2005

Two undergraduate laboratory experiments on the Hall effect are described in which the specimens are in the form of thin evaporated films. The first is concerned with the determination of the Hall coefficient and the mobility of conduction electrons in gold. The second describes the construction and the performance of magnetic fluxmeters made with bismuth films. Experimental data are given for a gold film 254 Å thick and for bismuth films ranging in thickness from 100 to 1430 Å.
An Extension of Euler's Theorem to Minkowski Space
Authors: Schwartz H. M.
Published: August 2005

A simple proof based on an elementary analysis of its eigenvalue problem is given of the reduction of the general element of the proper orthochronous Lorentz group to one of two possible standard forms. This represents the closest analog to Euler's theorem on rigid-body rotations.
Lorentz Transformation in the Undergraduate Curriculum
Authors: Romain Jacques E.
Published: August 2005

It is shown, in contradiction to an argument recently proposed by J. Sokoloff, that the commonly used derivation of the Lorentz transformation, based on the requirement for invariance of the propagation law of a light wavefront, is indeed valid in one dimension as well as in two or three. The point of interest is the necessity to take due account of the isotropy condition in one dimension.
Resonant Detection of Light Pressure by a Torsion Pendulum in Air—An Experiment for Underclass Laboratories
Authors: Pollock Robert E.
Published: August 2005

A mirror suspended by a torsion fiber in air may be driven at resonance by the force from an interrupted light beam to reach a detectable oscillation amplitude. The radiometer forces which compete with the true light force may be separated experimentally. The method was tested as a laboratory experiment by a small freshman class and proved to be workable and interesting to the students. The concrete experience with damped simple-harmonic motion and with small-signal detection techniques as well as the simplicity of the apparatus enhance the interest of this project as a teaching experiment.
Electron Velocity Distributions in Gases
Authors: Bowe Joseph C.
Published: August 2005

An analytical expression for the velocity-distribution function for the low-energy region (u < u1) is obtained from the Maxwell-Boltzmann transport equation on the assumption that inelastic collisions occur at u = u1. The exact linear differential equation that defines the distribution function in the high-energy (u > u1) region is also derived. The mathematical difficulties and the usual approximations that are associated with this equation are briefly examined. An approximate analytical solution is given in terms of Hankel functions of the first kind when the cross section for inelastic collisions is assumed to be proportional to (u − u1)γ. The theory, which is developed in an elementary formalism, applies to electrons that are in a uniform dc electric field. Physical interpretations and the effects of inelastic collisions are emphasized.
A Classical Analog for Relativistic Contraction
Authors: Epstein Lewis
Published: August 2005

It is possible to construct a mechanical model which demonstrates the Fitzgerald contraction. An equation is derived to describe the shape of a dimple moving across an elastic membrane, clearly showing the analogy to the field of a point charge in free space, including the relativistic contraction in the direction of motion. This model should suggest some reason to the inquiring mind that persists in wondering—“what really makes it shrink”.
An Inexpensive Optical-Lever Amplifier for Studying the Brownian Motion of a Galvanometer
Authors: White K. S.
Published: August 2005

A simple optical-lever amplifier constructed from components normally available in a university physics department is described. The design was based on one by Jones, but was modified so that it could be built by a final-year undergraduate. The amplifier was used to study the Brownian motion of a galvanometer. From this study, the value of Boltzmann's constant k was found to be (1.46±0.1) × 10−23J°K−1, the accepted value being 1.38 × 10−23J°K−1.
Poor Man's Mass Spectrometer
Authors: Dewdney John W.
Published: August 2005

A mass spectrometer has been designed around simple constituents: the vacuum system is made from copper plumbing parts; electrical leads into the vacuum are via darning needles pushed through rubber stoppers; the filament of the thermal ionization source is from a small light bulb; object and image slits are made from bits of razor blades sandwiched between brass washers. The magnetic field is supplied by a permanent magnet fitted with homemade cylindrical pole pieces (of such a diameter to give second-order direction focusing). A modest vacuum of 10−4 mm Hg is required. When the instrument is focused (by adjusting the position of the pole pieces) and aligned (by rotating greased rubber stoppers) a resolving power of 50 can be obtained.
Undergraduate Experiment on Elasticity of Rubber Bands
Authors: Papadakis Emmanuel P.
Published: August 2005

An experiment on the measurement of the elastic modulus of rubber is described. Both static and dynamic methods are used; the elastic modulus is found to be a function of strain and frequency. The experiment is useful since it illustrates several physical principles, introduces the student to deviations from Hooke's including relaxations, and costs very little.
Number of Energy Levels for a Debye-Hückel or Yukawa Potential
Authors: Holladay W. G. , Thomas Jess Brooks , Smith Charles Ray
Published: August 2005

For the exponentially shielded Coulomb potential, the WKB approximation to the Schrödinger equation has been used to determine N(l), the total number of bound states for a given angular momentum l; NT, the total number of bound levels; and lm, the maximum value of angular momentum l for a bound state. These results are somewhat at variance with previously published results, obtained by other methods.
Principles of p-n Junction Detectors
Authors: Brown Gordon M. , Clark Alan F. , Pluta Philip R.
Published: August 2005

Elementary band theory and impurity concentration effects are reviewed in order to derive the basic relations for barrier layer width and electrostatic potential as a function of applied reverse bias. Use of the solid-state ionization detector in the laboratory curriculum is indicated with sample lab experiments.
Dynamation
Authors: Holcomb D. F. , Cotts R. M.
Published: August 2005

A new word is proposed for addition to the English scientific vocabulary. The word is “dynamation,” which is defined as “time rate of change of momentum.” The associated regular verb is, in its infinitive form, “to dynamate” meaning “to change the momentum as a function of time.” It is believed that the use of a single word for these fundamental concepts of Newton-Einstein mechanics will significantly improve pedagogical technique in the teaching of mechanics. It is believed that the word will also tend to promote greater clarity, precision and economy of expression among scientists when discussing mechanical problems.
Undergraduate Research Project: Photon Diffraction
Authors: Biser Roy H.
Published: August 2005

Undergraduate research can be an important part of the program of a small physics department. An example is given in which optical diffraction is studied using photon-counting techniques.
Apparatus Drawings Project. Report Number 33. Simple Apparatus for Three Lecture Demonstrations
Authors: Williams T. Walley
Published: August 2005

This article describes three pieces of simple apparatus for lecture demonstrations: a model of Faraday's motor, apparatus for demonstrating the trajectory of a projectile, and an apparatus for demonstrating the conservation of angular momentum.
Conversations with Albert Einstein
Authors: Shankland R. S.
Published: August 2005

The following account of talks with Professor Einstein are the notes made by the writer in Princeton immediately after each of five visits about ten years ago. They were originally written without any thought of publication, but rather as a private record of very wonderful experiences. However, since they may contain matters of interest to others, it has been decided to publish them.
Yes, What Is Happening to Calculus?
Authors: Weinstock Robert
Published: August 2005

Aspects of the difficulties underlying physics teachers' concern at recent changes in calculus courses are presented. A suggestion for alleviating these difficulties is offered.
Apparatus Drawings Project. Report Number 30. Atomic Beam Apparatus for Determining the Mean Free Paths of Potassium Atoms in Argon
Authors: Marcley Robert G.
Published: August 2005

A simple atomic beam apparatus of special pedagogic interest, developed specifically for an introductory laboratory, is described. It consists of an electrically heated oven for vaporizing metallic potassium, a slit system for collimating a beam of the neutral atoms, and a detection system for measuring the number of atoms that traverse a path through an atmosphere of argon at reduced pressure. The slit-detector separation can be varied from about 2 to 20 cm. The system pressure can be adjusted from about 5×10−4 mm Hg to 5×10−6 mm Hg, and is determined with a conventional ionization gauge. The ion gauge control circuits, as well as the vacuum tube voltmeter for measuring the detector output, are low-cost “home-made” units. The relatively low-cost glass-metal apparatus is evacuated with a small 2-stage oil diffusion pump, and was designed to be operated with a minimum of maintenance. Eight pieces of the apparatus have been in regular use for four years. Detailed information on construction of the basic apparatus and the ancillary electronic equipment is given.
Anniversaries in 1963 of Interest to Physicists
Authors: Barr E. Scott
Published: August 2005

During the year 1963 there will be major anniversaries of the birth or death of thirteen men whose accomplishments and influence have been of importance to the development of physics. Brief accounts of their achievements and lives are given here.
A Simple Spring Gun: Experiments; Demonstrations
Authors: Rice Michael
Published: August 2005

A spring gun is described which is useful in experiments where an approximation of a point mass of known initial velocity is desired. The velocities imparted to a 34-in. steel ball range continuously to 12 m/sec and are reproducible to ±2%. The gun is of simple design, easily built in a departmental shop, and its dynamics readily understood. A brief description is given of uses which we have made of the gun both in instructional laboratories and in lecture demonstrations.
Quantum Mechanics of Beats between Weakly Coupled Oscillators
Authors: Meijer Paul H. E. , Tanaka Tomoyasu
Published: August 2005

Although the weakly coupled double pendulum seems to be a standard illustration in classical mechanics, it is seldom mentioned in quantum mechanics. It shares this fate with the damped harmonic oscillator, but while there is a good reason for avoiding the last one in quantum mechanics, the first can be treated with the same procedure as in classical mechanics. The exact solution is then compared with the solutions obtained by time-independent and time-dependent perturbation methods. It turns out that there are some additional steps to be taken, compared to the usual textbook treatment of the time-independent perturbation theory, due to the fact that all the levels of the unperturbed problem are degenerate. It is shown that the diagonalization of the secular matrix in the time-independent problem is equivalent to a problem of rotation of angular momentum operators in function space. The time-dependent problem needs, again, additional steps due to the degeneracy, and it yields the well-known beat-behavior.
Note on the Invention of Photometry
Authors: Middleton W. E. Knowles
Published: August 2005

It has been suggested that François d'Aguillon (1566–1617) made a photometer, thus anticipating Pierre Bouguer (1698–1758). It is shown that D'Aguillon was not trying to measure light, but only to find the law according to which light diminishes with the distance from its source. He did not succeed in this attempt.
Determination of the Quantum Numbers for the Levels of the 5461-Å Line in Hg
Authors: Flores Jorge Merlo
Published: August 2005

Through a relatively simple experimental setup the anomalous Zeeman pattern of the 5461-Å line of Hg can be analyzed. With the assumption that the coupling is of the type LS, and without exacting too much precision from the observations, it can be determined that the transition is of the type S13−P23.
Preparatory Curriculum for PSSC and Other Physics Programs
Authors: Deall Louis , Badar Lawrence
Published: August 2005

A laboratory-oriented introductory course for beginning high school students is described. Specially developed materials, including a device called the “category approach” to the use of mathematics in physical reasoning are discussed. Some techniques and materials from the PSSC Physics program have been incorporated. Vertical articulation of the entire science curriculum is achieved through this Introductory Physics course, Chemistry, PSSC Physics, and Advanced Placement Chemistry. A cyclic structuring of all concepts to replace needless repetition of topics has been effected. The present paper deals specifically with the development of the Introductory Physics course.
Billiard-Ball Collision Experiment
Authors: Bayes Jane Higginbotham , Scott William T.
Published: August 2005

A description is given of a simple device that makes possible quantitative experiments on billiard-ball collisions. Data are presented to show that the 90°-angle rule for collisions of two balls of equal mass can be verified if steel balls are used on a soapy glass surface. Indication is given of the effects of rolling and of inelasticity when plastic balls are used.
Displacement Currents and Magnetic Fields
Authors: French A. P. , Tessman Jack R.
Published: August 2005

The methods of calculating fields due to quasi-steady currents in closed and unclosed circuits are reviewed. It is emphasized that it is sufficient to apply the Biot-Savart law to all the moving charges and to ignore the vacuum displacement current. Attention is drawn to a basic error in the widespread practice of treating a circuit containing a capacitor as though the fringing fields could be ignored and the displacement current replaced by conduction currents confined to the gap between the plates.
Fokker-Planck Equation
Authors: Desloge Edward A.
Published: August 2005

The Fokker-Planck approximation to the interaction term in the Boltzmann transport equation is discussed. For the case of binary collisions a simple derivation of this term is presented. The resultant expressions for the associated quantities 〈Δvi〉 and 〈ΔviΔvi〉 are evaluated for the case of a fully ionized gas. Several forms of the distribution function are considered.
Classical Distribution of a Mutually Interacting System of Particles
Authors: Barlow Carl A.
Published: August 2005

It is shown that subject to very general conditions which do not exclude strong or velocity dependent interactions but which tend to restrict consideration to systems having only long range forces, the most probable distribution of an assembly of interacting particles is classically given exactly by a Boltzmann distribution in which appears in the Boltzmann factor a term identical to an interaction with the associated most probable self-consistent field.
Possibility of Observing the Magnetic Charge of an Electron
Authors: Harrison Halstead , Krall Nicholas A. , Eldridge O. C. , Fehsenfeld F. , Fite Wade L. , Teutsch Werner B.
Published: August 2005

The Lorentz force law and Maxwell's equations are extended to include magnetic as well as electric charges, by requiring that the equations be symmetrical in these charges. This extension predicts that the absolute magnetic charge of a particle cannot be detected. What can be detected are differences in magnetic charge between elementary particles and the validity of the assumed method of extending the Maxwell-Lorentz equations. An experiment is described which appears to measure the magnetic charge of an electron, but which instead bears on the form of the Maxwell-Lorentz equations. Other arguments limit the difference between proton and electron magnetic charges.
Acceptable Solutions and Boundary Conditions for the Schrödinger and Dirac Equations
Authors: Armstrong Baxter H. , Power Edwin A.
Published: August 2005

It is shown that the condition of finiteness at the origin, usually imposed on solutions to the nonrelativistic Schrödinger equation for the hydrogen atom (and some other systems) is not necessary. The quadratically integrable l = 0 “anomalous” solution which is usually excluded in this fashion is not a solution to the Schrödinger equation at the origin, and consequently does not need to be excluded by a boundary or other type condition. The relativistic generalization through the Dirac equation of this anomalous solution is not quadratically integrable. The solution generalized according to the relativistic Schrödinger equation is quadratically integrable and obeys the equation at the origin. Consequently, a boundary or other type condition may still be needed in a general relativistic theory.
Accelerating Frames of Reference and the Clock Paradox
Authors: Lass Harry
Published: August 2005

The Lorentz-Einstein transformations are obtained by a method which enables one to derive a coordinate transformation between an inertial frame of reference and a noninertial accelerating system. With the aid of this transformation, one computes the explicit time for the round trip of the noninertial twin who leaves the inertial twin with initial speed −V, and returns by means of an acceleration. It is found that the accelerating twin returns younger than the inertial twin.
Remarks on the Bound States of a Central Potential in Quantum Mechanics
Authors: Downs B. W.
Published: August 2005

A simple proof is given of the fact that the ground state of a central potential is an S state. The ordering of the bound states of a central potential according to the value of the angular momentum and the number of nodes of the solution to the radial Schroedinger equation is also discussed.
Caustic of the Primary Rainbow
Authors: McDonald J. E.
Published: August 2005

An instructive problem in the geometrical optics of caustics is afforded by the classical theory of the rainbow. Since any caustic may also be viewed as a cusp locus of wavefronts, the same problem has bearing on certain aspects of the diffraction theory of the rainbow. Using a method of caustic analysis capable of delineating the complete emergent caustic of the primary rainbow, it is shown that past conceptions of the full caustic locus have been markedly in error. The correct locus is found to exhibit an odd cusp on a segment of the (virtual) caustic lying wholly within the raindrop.
Physics in a Toy Boat
Authors: Finnie I. , Curl R. L.
Published: August 2005

A method of propulsion commonly used in toy boats consists of a shallow chamber, covered by a thin diaphragm, which is connected to the water astern of the boat by pipes. Filling the chamber with water and then heating it's base leads to vigorous self-induced vibration of the diaphragm and water column in the pipes with resulting forward motion of the boat. The paper describes the mechanisms of self-induced vibration and of propulsion. It is shown that this inexpensive toy demonstrates a number of physical principles and provides opportunities for further research.
Solution of the Stokes Flow of a Sphere by Minimization of the Dissipation of Energy
Authors: DuPont Kenneth C. , Rosen Philip
Published: August 2005

A detailed derivation of the velocity flow field of a sphere moving slowly through an incompressible viscous fluid of infinite extent (Stokes' flow) can be accomplished by simultaneously satisfying the equations of motion and continuity for the fluid particles. An alternate method is used here which makes use of Onsager's principle of least dissipation of energy. To simplify the problem a constant velocity U equal and opposite in direction to the velocity of the sphere is superposed on the system to allow the fluid to flow slowly in the +x direction past the now stationary sphere. A variational problem is then stated and a Euler-Lagrange equation is obtained, the solution of which specifies the velocity flow field dependence on r, the distance from the center of the sphere.
Iodine Source for Half-Life Experiments
Authors: Moore Frank L.
Published: August 2005

Sodium iodate is a very satisfactory material for half-life experiments. The single stable isotope of iodine has a neutron capture cross section of 6 barns. The radioisotope has a half-life of 25 min allowing counting over several half-lives in a laboratory period. With two hour irradiation the 15-h sodium activity is negligible, whereas with long irradiation, the sources are suitable for a mixed decay experiment.
Radiance
Authors: Nicodemus Fred E.
Published: August 2005

Wide generality for optical radiometry can be achieved by treating the basic radiometric quantities as field quantities. The treatment is that of classical ray optics, with emphasis on the geometrical relations involved. It is shown that radiance, defined as N ≡ ∂2P∂Ω cosθ∂A [W·cm−2·sr−1], the radiant flux or power per unit solid-angle-in-the-direction-of-a-ray per unit projected-area-perpendicular-to-the-ray, has the same value at any point along this ray within an isotropic medium, in the absence of losses by absorption, scattering, or reflection. More generally, the quantity N/n2 (where n is the index of refraction of the medium) in the direction of a ray is shown to be invariant along that ray, even across a smooth boundary between different lossless media. The usefulness of this invariant property of radiance is illustrated by examples of practical applications.
Special Nature of Orbital Angular Momentum
Authors: Louck James D.
Published: August 2005

The properties of orbital angular momentum operators are examined within the framework of the formal theory of angular momentum. It is demonstrated that the occurrence of only integral quantum numbers in the orbital theory is a consequence of the particular form of the orbital operators. Single-valuedness of the eigenfunctions need not be postulated.
Stress Effects due to Lorentz Contraction
Authors: Dewan Edmond M.
Published: August 2005

Relativistic stress effects caused by the Lorentz contraction described in a previous publication are related to implications of relativistic simultaneity. This relationship is discussed here, in some detail, in order to clarify certain pedagogically difficult aspects of the problem. Objections raised in a recent Note are also answered.
Unipolar Machines. Association of the Magnetic Field with the Field-Producing Magnet
Authors: Das Gupta A. K.
Published: August 2005

In this paper, various experiments are described which prove that in unipolar machines, if the field-producing magnet is rotated, the field does not rotate but remains stationary. If the field-producing magnet is solidly fixed with the rotor and both are rotated, a voltage is generated in the rotor which is practically equal to the voltage generated in the same rotor when rotated at the same speed in the field of the stationary magnet. Similarly, if current is passed through the rotor when the rotor is solidly fixed with the magnet, a torque is generated which is practically equal to the torque generated in the same rotor when the magnet is kept stationary.
S-Matrix Solution for the Forced Harmonic Oscillator
Authors: Fuller R. W. , Harris S. M. , Slaggie E. Leo
Published: August 2005

The exact solution for a forced, undamped quantum harmonic oscillator is obtained by S-matrix techniques. The force F(t) is assumed to vanish at t = ±∞. The only restriction is that the Fourier transform of F(t) must exist. The transition probabilities are obtained in closed form in terms of Laguerre polynomials. The mean energy transfer to the oscillator is found to be independent of the initial state and is in agreement with the classical result for an oscillator originally at rest. This problem provides a good example of field theoretical procedures in an elementary context. Therefore, all field theoretical concepts are carefully defined and explained as they are introduced in order that the discussion may be self-contained.
A Note on Fermi Levels, Quasi-Fermi Levels, and Terminal Voltages in Semiconductor Devices
Authors: Jordan A. G. , Lade R. W. , Scharfetter D. L.
Published: August 2005

The concepts of electrostatic and electrochemical potentials as they bear on the volt-ampere characteristics of semiconductor devices are reviewed. The meaning of voltage drops across portions of semiconductor materials containing excess carriers is clarified. The relation between voltage readings obtained with probes and the different potentials existing in the material is discussed.
Cosmology, Mach's Principle and Relativity
Authors: Dicke R. H.
Published: August 2005

The significance of Mach's principle (and the implicit relativity principle) for field theory is discussed, also the significance of zero-mass boson fields for the geometry of the physical space. The significance of such fields for Mach's principle within the framework of cosmology is also discussed. It is suggested that the distant matter of the universe generates one or two zero-mass boson fields, very likely a tensor field and perhaps a scalar, and that each of these fields propagates, carrying into the laboratory a quasistatic influence having its origin primarily in the distant matter of the universe. The observable effects of these “Machian fields” are described.
A Geometric Representation of Lorentz Frames for Linearly Accelerated Motion
Authors: Brehme Robert W.
Published: August 2005

The orthogonal-axes method of representing events between two different Lorentz frames in uniform motion is extended to the case in which one of the frames is accelerated. The accelerated space ship is used as an example.
Floating of a Long Square Bar
Authors: Reid Walter P.
Published: August 2005

Positions of stable equilibrium are determined for the case of a long square bar floating on a liquid. It is found that the bar might float in any angular position, depending upon the density of the liquid. For high or low liquid densities, the bar floats with two sides parallel to the surface of the liquid. For a range of intermediate densities, it floats with all sides making angles of 45° with the liquid surface.
Slow-Motion Moment of Inertia Apparatus
Authors: Weltin Hans
Published: August 2005

From scrap hardwood, silk thread, and bits of wire, a moment of inertia apparatus has been assembled, which gives experimental results that compare favorably with those obtained from the most expensive commercial equipment. Its special advantages are slow motion and the illustration of viscous drag caused by air friction.
Schiff's Charges and Currents in Rotating Matter
Authors: Webster David L.
Published: August 2005

Schiffs equations for fictitious charges and currents to be used with rotating axes of coordinates, written by him for fields in vacuum, are written here for fields in material media and are illustrated with examples.
Growth of Hexamethylenetetramine Crystal from Vapor: A Laboratory Experiment
Authors: Veigele Wm. J.
Published: August 2005

A technique is described for growing single crystals of (CH2)6N4 from a vapor using simple techniques and apparatus normally found in college physics laboratories. The method is suitable for an experiment in either graduate or undergraduate laboratory.
Scattering Theory and Adiabatic Switching
Authors: Haller Kurt
Published: August 2005

An elementary procedure for deriving the Born (Liouville-Neumann) series for the transition amplitude for elastic scattering is developed. It is shown that the use of adiabatic switching eliminates the difficulties of energy nonconserving transitions and ambiguously defined improper integrals, which are usual in elementary treatments in textbooks.
Two Theorems Concerning the Laplace Operator
Authors: Pomeranz Kalman B.
Published: August 2005

A theorem is derived which gives the mean value of a well-behaved function in a small spherical volume in terms of the value of the function and its Laplacian at the center of the sphere. The magnitude of ψ(x,y,z) at the center exceeds the mean value at neighboring points or falls short of the mean value according to whether −∇2ψ is positive or negative.
On the Way to Open-Ended Experiments for Physics Majors
Authors: Friedmann G.
Published: August 2005

The working of a senior laboratory lying between the extremes of fully predetermined experiments on the one hand and fully “open-ended” experiments on the other is described. It is concluded that such a laboratory is the logical bridge to train students towards careers in research.
Transport Properties of a Simple Gas
Authors: Desloge Edward A.
Published: August 2005

The coefficients of diffusion, viscosity, and, thermal conductivity of a simple gas are calculated by expanding the distribution function in Hermite polynomials, and obtaining an approximate solution to the Boltzmann transport equation. The techniques employed result in a number of simplifications of the usual derivations.
Fermi Statistics of Two-Dimensional Free-Electron Systems
Authors: McKelvey J. P. , Pulver E. F.
Published: August 2005

The variation of the Fermi energy with temperature and free-particle concentration is calculated analytically for a number of two-dimensional systems, including the free-particle gas, the intrinsic semiconductor and the impurity semiconductor. These illustrations, while, of course, applicable to certain physically realizable systems, are also of considerable illustrative and pedagogical interest, since the integrals which are involved can invariably be worked out in closed form. The Fermi energy as a function of temperature and concentration may then in some cases be calculated in closed form, while in others it is obtained implicitly as the solution to a fairly simple transcendental equation. The physical significance of the variation of Fermi energy as a function of temperature and concentration is discussed, and the deviation of the n0p0 product for the two-dimensional semiconductor from the Boltzmann mass-action result is calculated and discussed in detail. The conditions corresponding to the failure of the Boltzmann approximation and the onset of degeneracy are outlined. Application of the calculational methods to simple Bose-Einstein systems is briefly treated.
Point Defects—An Evaluation
Authors: Huntington H. B.
Published: August 2005

The current state of understanding of point defects is reviewed from the standpoint of theoretical models and experimental findings. Because of the inherent difficulties with most high-temperature equilibrium measurements of lattice defects, the experimental effort has largely been focused on the generation of excess defects by quenching, cold work, and radiation damage. The so-called five stages for the annealing of excess defects are discussed in some detail with attempt to point out where there has been substantial progress in understanding and where strong controversy still persists. Of these latter perhaps, the most outstanding example is the nature of the stage III annealing. In many cases the release of interstitials from traps at dislocations and impurities must play a role. Di-interstitial migration is a tempting possibility but recent experiments indicate a primary character for the defect mobile at this stage.
Complexions of an Assembly of Quasi-Independent Localized Systems
Authors: Trevena D. H.
Published: August 2005

The total number of complexions of an assembly of quasi-independent localized systems is equal to the sum of a large number of terms. It is usually assumed that only the greatest term in this sum makes any significant contribution to the sum. A simple way of illustrating the increasing accuracy of the assumption with increasing numbers of systems is considered in this paper.
Emission Spectroscopy as an Elective for Science Majors and Engineers
Authors: Peters J. Theodore
Published: August 2005

This is a condensation of a paper given at the Physics Section Meeting of the American Association for the Advancement of Science in Philadelphia, 29 December 1962, by J. Theodore Peters and M. Lalevic of the Drexel Institute of Technology.

A plea is made for more colleges and universities to offer emission or atomic spectroscopy as an undergraduate elective. So much of our knowledge today of the mechanism of radiation, of atomic structure, and of properties of atomic nuclei resulted from spectroscopic research. It seems only natural then to expect more course offerings in this field. Further evidence is given for the need for more work in higher reaches of theoretical spectroscopy. There is still much to be discovered and checked and tabulated as to emission lines for many of the 102 elements.
Resource Letter NS-1 on Nuclear Structure
Authors: Preston M. A.
Published: August 2005

Prepared at the request of the AAPT Committee on Resource Letters; supported by a grant from the National Science Foundation.

This is one of a series of Resource Letters on different topics, intended to guide college physicists to some of the literature and other teaching aids that may help them improve course contents in specified fields of physics. No Resource Letter is meant to be exhaustive and complete; in time there may be more than one letter in some of the main subjects of interest. Comments and suggestions concerning the content and arrangement of letters as well as suggestions for future topics will be welcomed. Such communications should be sent to Professor Arnold Arons, Chairman, Resource Letter Committee, Department of Physics, Amherst College, Amherst, Massachusetts.

Notation: The letter E after an item number indicates elementary level, useful principally for freshman liberal arts through sophomore physics courses; the letter I indicates intermediate (junior, senior) level; and the letter A indicates advanced material principally suited for senior, graduate study. An asterisk (*) indicates items particularly recommended for introductory study.

Additional copies: Available from American Institute of Physics, 335 East 45 Street, New York, New York 10017. When ordering, request Resource Letter NS-1 and enclose a stamped return envelope.
Physics in the Elementary Grades
Authors: Chamberlain Owen
Published: August 2005

The following six papers were presented at a symposium at the Thirty-Third Annual Meeting of the American Association of Physics Teachers on 24 January 1964, in New York. The symposium was sponsored by the Association's Committee on Elementary Science. The program was arranged and the papers were collected by Robert Karplus, chairman of the committee. Owen Chamberlain served as chairman of the session.
Relationships of Wave Packet Variances
Authors: Holze Dick H. , Scott William T.
Published: August 2005

Some results of interest in quantum measurement theory are derived from a consideration of a collision between two one-dimensional Gaussian wave packets. Relationships are found between the momentum and position uncertainties of the packets before and after the collision. It is shown that the coordinates of a poorly defined packet can be better defined by causing it to collide with a well-defined packet. A classical analog is presented in which the same results are obtained.
An Advanced Undergraduate Laboratory Experiment for Studying the Motion of Forced Vibration
Authors: Bueche F. , Pavelka C.
Published: August 2005

An advanced undergraduate laboratory experiment which studies the response of a bar to forced transverse vibrations is described. The amplitude and phase of vibration are monitored using a relatively simple optical system involving Moire fringes. Light is passed through two Ronchi rulings onto a photocell, the photocell output being a direct measure of the phase and the amplitude of vibration. The photocell output and the oscillator voltage used to drive the bar can be applied to the vertical and horizontal input, respectively, of an oscilloscope to produce Lissajous figures. These figures can then be studied and related to the properties of forced vibration. Typical results for resonance curves with and without external damping are given.
Free Energy in Magnetostatic or Electrostatic Fields
Authors: Plesset Milton S. , Venezian Giulio
Published: August 2005

The forces acting on a body, and its position of equilibrium, in a uniform magnetic or electric field are determined by the free energy and not by the field energy. Incorrect results are obtained if the field energy is used as a potential function since the work done in a virtual displacement on the distant sources of the field is not taken into account. The net-energy flux that results from a virtual displacement of a body is calculated here and the free energy is determined. It is shown that the flux of the Poynting vector cannot be neglected in this case even though quasistatic processes are involved. The results are illustrated by the example of a paramagnetic or a diamagnetic ellipsoid in a uniform magnetic field.
Millikan—Teacher and Friend
Authors: Neher H. V.
Published: August 2005

Editors Note: As a result of support by Addison-Wesley Publishing Company, the American Association of Physics Teachers has established an annual lectureship, named in honor of Robert A. Millikan. It is anticipated that this will bring to each summer meeting of the Association a physicist who will speak on a topic of current interest and that the summer meeting will thus have a feature comparable with the Richtmyer Lecture at the annual meeting. The committee responsible for the first Millikan Lecture chose H. V. Neher, long time associate of Millikan. This highly suitable choice was as appropriate as was Neher's choice of a topic—Millikan himself. The editors of the American Journal of Physics are grateful for permission to publish this pleasantly informal biographical lecture, spiced as it is with personal reminiscences.
A Laboratory Demonstration of the Equivalence of Potential Energy and Work
Authors: Zinke Otto Henry
Published: August 2005

A laboratory experiment is described which demonstrates the equivalence of potential energy and work to an accuracy of several per cent through the use of two magnets.
Electromagnetic Relations in a Single Coordinate System
Authors: Pugh Emerson M.
Published: August 2005

Certain experimental phenomena, like the homopolar generator, whose analyses have caused confusion are shown to be understandably treated by the following: Use the differential form of Maxwell's four field relations together with the Lorentz force equation as the fundamental relations for treating all electromagnetic phenomena in the observer's coordinate system. The Lorentz force is considered to act on all of the charges in any material body moving in magnetic fields in these coordinates. Faraday's law ε = −dΦ/dt, becomes a derived through very useful relation. This system provides revealing Poynting vector for all steady-state energy conversions.
Open-Ended Problem Instruction in General Physics
Authors: Lerman Noah
Published: August 2005

Despite the undisputed importance attached to problem-solving activities in college and university physics courses, problem teaching methods have changed little since 1900. A possible explanation of this paradoxical combination of importance and stagnation is lack of awareness of the tremendous range of activities that problem work could provide for teaching students the skills and attitudes of creative physicists—if taught in a way very different from the usual methods of today. The plausibility of this explanation is enhanced by the critique of current problem teaching methods presented in this paper. Present-day methods are evaluated on the basis of six specific objectives of physics-problem teaching, derived from an analysis of the skills and attitudes involved when a creative physicist tackles a problem in his own work. It is shown that conventional methods aim at only one of these six objectives. A new approach, making use of open-ended problems and designed to attain all six objectives, is presented. It is illustrated by a detailed teaching sample and additional procedural remarks, in order to facilitate experimentation with the method.
Experiments on Film in the Elementary Physics Laboratory
Authors: Rogers D. H.
Published: August 2005

The successful use of three films: Momentum of Electrons, The Ultimate Speed, and Time Dilation as “experiments” in the second year Physics Laboratory is described. The regular experiments in the laboratory are used to teach experiment design, measurement, and error calculation; and the film experiments were used to show how real physicists designed and performed their experiments using the same principles. The films also permitted the “use” of equipment not normally available to second-year students. Working in pairs, the students viewed the films, took data from the instruments shown, estimated the error in the measurements, then wrote up the experiment as a normal laboratory report. While the use of Momentum of Electrons as an “experiment” was not as successful as was this use of the other two films, the class was enthusiastic over all three films, and was unanimous in wanting at least one film experiment of this type each year.
Michelson-Morley Experiment
Authors: Shankland R. S.
Published: August 2005

The Michelson-Morley experiment, performed in Cleveland in 1887, proved to be the definitive test for discarding the Fresnel aether hypothesis which had dominated physics throughout the 19th century. The experiment had been suggested to Michelson by his study of a letter of James Clerk Maxwell, and a preliminary but inconclusive trial had been made at Potsdam in 1881. It seems certain that the experiment would never have been repeated except for the urging of Kelvin and Rayleigh at the time of Kelvin's Baltimore Lectures in 1884, which Michelson and Morley attended. The conclusive null result of the Cleveland experiment was decisive in its influence on Lorentz, FitzGerald, Larmor, Poincaré, and Einstein in developing their theories of the electrodynamics of moving bodies, which culminated in the special theory of relativity. The present account contains material from extensive notes and correspondence related to the work of Michelson and Morley which the writer has assembled during the past years.
A Study of the Discovery of Fission
Authors: Sparberg Esther B.
Published: August 2005

Nuclear fission was discovered twenty five years ago by Hahn and Strassmann. Was the road to the discovery as torturous as some have contended? The roots are examined; the surprising climax and its impact are described. Some scientists have commented on the discovery in retrospect. The discovery of fission is scrutinized both in the light of these comments, and of the general characteristics of scientific discovery.