摘要:

The plane‐wave electromagnetic fields for a kicked sheet of charge are found and then compared with the fields obtained by superimposing the radiation fields of the individual charges in the plane. Unlike the case of the oscillating sheet of charge discussed inTheFeynmanLecturesonPhysics,Vol.I[R. P. Feynmanetal. (Addison‐Wesley, Reading, MA, 1963)], the plane‐wave fields of the kicked sheet differ from the fields obtained by superposition of the individual radiation fields. The resolution of this problem requires consideration of relativistic effects even though the velocity of the sheet after the kick may be as small as desired. The relation between the solution for the kicked sheet and solution for the oscillating sheet is discussed, and it is shown how the two solutions are consistent if all contributions to the fields are taken into account.

ISSN:0002-9505    

DOI:10.1119/1.14663

出版商:American Association of Physics Teachers    

年代:1986

数据来源: AIP

摘要:

It is shown that special relativistic mechanics, when augmented by a particular version of the equivalence principle, predicts essentially the same numerical value as does the general theory for the precession anomaly of the planet Mercury. A possible laboratory experiment to test this version of the equivalence principle is discussed.

ISSN:0002-9505    

DOI:10.1119/1.14664

出版商:American Association of Physics Teachers    

年代:1986

数据来源: AIP

摘要:

Galileo’s earliest telescopic measurements are of sufficient quality that their detailed analysis yields scientifically interesting and pedagogically useful results. An optical illusion strongly influences Galileo’s observations of Jupiter’s moons, as published in theStarryMessenger. A simple procedure identifies individual satellites with sufficient reliability to demonstrate that Galileo regularly underestimated satellite brightness and overestimated elongation when a satellite was very close to Jupiter. The probability of underestimation is a monotonically decreasing function of separation angle, both for Galileo and for viewers of a laboratory simulation of the Jupiter ‘‘starfield’’ viewed by Galileo. Analysis of Galileo’s records and a simple simulation experiment appropriate to undergraduate courses clarify the scientific problems facing Galileo in interpreting his observations.

ISSN:0002-9505    

DOI:10.1119/1.14638

出版商:American Association of Physics Teachers    

年代:1986

数据来源: AIP

摘要:

This article gives a combined form of the laws of Ampere and Biot–Savart which allows us to calculate the infinitesimal magnetic circulation around a closed loop ∑δB⋅δlin terms of the current flowithrough an infinitesimal current path δs, and the change in the solid angle subtending the closed loop δΩ as the apex of the solid angle traverses δs:∑δB⋅δl=iδΩ×10−7. After giving its derivation from the law of Biot–Savart, the combined form is applied to a variety of magnetostatic problems. The illustrative examples, none of which requires the use of calculus for its solution, include the usual introductory course examples such as determining the magnetic field inside a toroidal coil, and at the center and along the axis of a circular current loop. In addition, the potentialities of the combined law are demonstrated by determining the field anywhere in the plane and along the axis of a rectangular current loop. Appendices include discussions of solid angles and relativistic effects.

ISSN:0002-9505    

DOI:10.1119/1.14639

出版商:American Association of Physics Teachers    

年代:1986

数据来源: AIP

摘要:

The question of how long it takes an inverted point‐mass pendulum to fall according to classical, semiclassical, and quantum theories is examined. The semiclassical analysis is based on the uncertainty introduced by measurement.

ISSN:0002-9505    

DOI:10.1119/1.14640

出版商:American Association of Physics Teachers    

年代:1986

数据来源: AIP

摘要:

A Monte Carlo calculation is described for the scattering and absorption of nonrelativistic electrons moving through a slab of uniformly distributed material of given atomic number, density, and thickness. We give an elementary discussion of the basic physics necessary for developing a computer simulation of the movement of electrons through the material. A basic program was written for microprocessors which determines backscattering, transmission, and absorption coefficients, and provides the user with a graphical output of the electron trajectories. We present the results of several simulations utilizing a moderate number of electrons. Such an approach might be used to teach intermediate to advanced students the physics of electron scattering. Several excercises are suggested for students who wish to pursue such problems in more depth.

ISSN:0002-9505    

DOI:10.1119/1.14641

出版商:American Association of Physics Teachers    

年代:1986

数据来源: AIP

摘要:

Based on the Feynman–Hellmann theorem, a new proof of the quantum virial theorem is presented. The same approach is also used to derive the virial formulation in relativistic quantum mechanics and for the case where the vector potential exists.

ISSN:0002-9505    

DOI:10.1119/1.14642

出版商:American Association of Physics Teachers    

年代:1986

数据来源: AIP

摘要:

A simple experiment for the demonstration of percolation problems is reported. Following the method of Last and Thouless [B. J. Last and D. J. Thouless, Phys. Rev. Lett.25, 1719 (1971)], measurements were performed on a sheet of conducting paper after randomly cutting out small square ‘‘sites’’ at a concentration 1−p. The conductance and the area fraction covered by the ‘‘infinite cluster’’Pwere then evaluated as a function ofp. This experiment, carried out at an undergraduate physics laboratory, appears to be appropriate as an introduction to the teaching of phase transitions.

ISSN:0002-9505    

DOI:10.1119/1.14643

出版商:American Association of Physics Teachers    

年代:1986

数据来源: AIP

摘要:

A variational principle is presented, by means of which the equation of motion of the damped harmonic oscillator is found. Starting from this variational principle a systematic reformulation of the classical mechanics leads us to a Hamilton–Jacobi equation with an additional term, which is proportional to the action. The quantization of this Hamilton–Jacobi equation, following a method originally due to Schrödinger, gives the Langevin–Schrödinger equation.

ISSN:0002-9505    

DOI:10.1119/1.14644

出版商:American Association of Physics Teachers    

年代:1986

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.14645

出版商:American Association of Physics Teachers    

年代:1986

数据来源: AIP