摘要:

A ball rolled down the tube of this apparatus is launched upward at various elevation angles as a projectile. Using as data the heights of three points on the tube, the student must consider potential energy, linear and rotational kinetic energy, frictional corrections, and projectile motion to predict the impact point of the ball.

ISSN:0002-9505    

DOI:10.1119/1.1941836

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

The analogy between the one-group theory of nuclear chain reacting systems and vibrating strings (or membranes) with similar geometry and boundary conditions is developed and some examples are considered. This should be useful as a class demonstration and may also help to give an idea of reactor buckling of assemblies with complex geometry.

ISSN:0002-9505    

DOI:10.1119/1.1941837

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

This paper presents a treatment of quantum-mechanical scattering suitable for a senior level course in modern physics. The entire treatment is based on the use of wave packets instead of unrealistic plane waves. The asymptotic behavior of the scattered wave packet is derived from physical considerations, and the Born approximation is then obtained for a wave packet in a manner which displays the details of the scattering process.

ISSN:0002-9505    

DOI:10.1119/1.1941838

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

The condition for diffraction of x rays is the coincidence of a reciprocal lattice point with the circumference of the reflecting circle. A mechanical-optical analogy is used to illustrate the genesis of single-crystal diffraction patterns.

ISSN:0002-9505    

DOI:10.1119/1.1941839

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

A description is given of the magnetic mirror effect exhibited by charged particles spiralling into a converging magnetic field. The apparatus makes use of a commercial electron tube filled with an inert gas, originally designed for measuring the specific charge of the electron. The necessary field configuration is provided by an ordinary bar magnet. Measurements of pitch angle at various points of the particle trajectories were made from photographs of the spiral orbits. The magnetic field strength corresponding to these points was determined independently from extensive field measurements carried out near the end of the bar magnet. The ratio of field strengths at two different points of the particle trajectory as a function of the spiral pitch angles at those points is compared with theory.

ISSN:0002-9505    

DOI:10.1119/1.1941840

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

In absence of all foreign materials or wall surfaces, phase transitions of the type vapor-to-liquid or liquid-to-solid are blocked by an activation-free-energy barrier. The latter arises from surface-free energy increases resulting from appearance of embryos of the more condensed phase. The thermodynamics of this type of phase transition are examined in Part I for the particular case of vapor condensation, a case for which theory and experiment now stand in tolerably good agreement. In Part II, kinetic aspects will be considered.

ISSN:0002-9505    

DOI:10.1119/1.1941841

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

Henry Augustus Rowland was born in Honesdale, Pennsylvania, in 1848, into a family of ministerial tradition, but he himself at an early age displayed an inclination toward and precocious gift for scientific experiment. The first twenty-seven years of his life were spent in self-preparation for a scientific career, although formally trained as a civil engineer at Rensselaer Polytechnic Institute, where he also taught physics. In 1875 occurred his “discovery” by Daniel C. Gilman, founder and first President of the new Johns Hopkins University, then in search of a suitable faculty. Now came his great opportunity, which Rowland eagerly seized upon, to spend a year in Europe, on salary from Johns Hopkins. Rowland's zealous and rewarding exploitation of this opportunity is the theme of this article. Rowland's letters and travel journal supply abundant material revealing how he traveled widely across Europe from Ireland to France, to Germany, Switzerland and Austria, and everywhere he visited the physical laboratories. He met many of the European men of science, inspected their facilities, and actually performed an important experiment in electromagnetism in Helmholtz's laboratory in Berlin. His critical commentary provides a unique survey of the state of physics in Europe at this time. In May, 1876, Rowland returned to America, unusually well-informed and self-assured, to assume the responsibilities of his new position as the first professor of physics in the Johns Hopkins University, where he built a distinguished scientific career for himself, broken off unhappily by his premature death in 1901.

ISSN:0002-9505    

DOI:10.1119/1.1941842

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

We study the most general unitary transformation that transforms the Hamiltonians of particles of spins 0,12, or 1, into Hamiltonians containing even or odd matrices only. We present also the expressions for the position operators for each transformation that are valid for the three kinds of particles mentioned above.

ISSN:0002-9505    

DOI:10.1119/1.1941843

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

A demonstration of the diffraction of a beam of electrons by a thin film of gold is constructed inside a black-and-white television tube. A pattern of concentric diffraction rings around a central maximum appears on the screen of a tube in which a thin gold film has been inserted in front of the electron beam. Since the two brightest of these can be seen clearly from a distance of at least forty feet in a darkened lecture room, the demonstration is suitable for large audiences.

ISSN:0002-9505    

DOI:10.1119/1.1941844

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP

摘要:

The relations between the ordinary density matrix, the density matrix in the coordinate representation, the Löwdin density matrices, the Dirac density matrix, and other density matrices are traced. The roles of pure and mixed cases, equilibrium and nonequilibrium situations, and single- and many-body representations are considered.

ISSN:0002-9505    

DOI:10.1119/1.1941845

出版商:American Association of Physics Teachers    

年代:1962

数据来源: AIP