ISSN:0002-9505    

DOI:10.1119/1.1986047

出版商:American Association of Physics Teachers    

年代:1971

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1986048

出版商:American Association of Physics Teachers    

年代:1971

数据来源: AIP

摘要:

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.)

ISSN:0002-9505    

DOI:10.1119/1.1986049

出版商:American Association of Physics Teachers    

年代:1971

数据来源: AIP

摘要:

We show, in an elementary but apparently new way, that the ratio of the energy to the frequency of a simple harmonic oscillator is an adiabatic invariant. The adiabatic invariance is a consequence of the conservation of angular momentum in the two-dimensional system, of which the one-dimensional harmonic oscillator is the projection. We also briefly discuss the connection between the quantization of angular momentum and the quantization of the oscillator's energy.

ISSN:0002-9505    

DOI:10.1119/1.1986050

出版商:American Association of Physics Teachers    

年代:1971

数据来源: AIP

摘要:

An astronomy course can demonstrate to the nonscientist that science is a human endeavor, involving social judgments and philosophical implications as well as established facts.

ISSN:0002-9505    

DOI:10.1119/1.1986051

出版商:American Association of Physics Teachers    

年代:1971

数据来源: AIP

摘要:

A one semester introductory physics course for physical science students emphasizes experimental involvement. PSSC physics and introductory calculus are prerequisite. The first two of three topics concentrate on the properties of the electron, positron, and photon. In the third topic the concepts developed in the previous topics are used to explain the structure of metals, emphasizing the role of defects. In an effort to give students an appreciation for the experimental apparatus of contemporary physical science and to illustrate the ease and speed with which some experimental results can be obtained, relatively sophisticated equipment was used. A detailed discussion of this course and its objectives is given as well as the results of student evaluation. This course has been offered and evaluated twice with encouraging results.

ISSN:0002-9505    

DOI:10.1119/1.1986052

出版商:American Association of Physics Teachers    

年代:1971

数据来源: AIP

摘要:

These recollections were written at the request of the Project on the History of Recent Physics of the American Institute of Physics.

ISSN:0002-9505    

DOI:10.1119/1.1986053

出版商:American Association of Physics Teachers    

年代:1971

数据来源: AIP

摘要:

It is shown how a diagram of two different inertial reference frames, representing the situation at a given instant from the viewpoint of one of the frames, can be used to develop insight into the various space-time effects of special relativity. An analysis is given of a number of thought experiments in which each frame makes its own measurements of various properties and then watches the other frame make similar measurements, Each frame can then interpret the data of the other frame. Measurements of relative speed, speed of light, Lorentz contraction, and time dilation are discussed in this way. Also, the same approach is used to consider causal difficulties arising from the possible existence of faster-than-light particles (tachyons).

ISSN:0002-9505    

DOI:10.1119/1.1986054

出版商:American Association of Physics Teachers    

年代:1971

数据来源: AIP

摘要:

This paper describes another approach to the photoelectric measurement ofh/ewhich is practicable for the introductory laboratory. The method owes its success to a new way of minimizing photoemission by the anode. A common vacuum photocell (1P39) and slit replace the eyepiece and cross hairs of a student grating spectrometer, illuminated by an ac mercury arc. If the cell is favorably oriented to the incident light, photoemission by the anode at high cathode retarding potential (6 V) can be reduced to less than 0.4% of the maximum photocurrent with zero retarding potential at the 3650-Åline. The 120-Hz component is amplified and rectified for presentation on a 100 μA dc meter. The maximum gain is sufficient to indicate full scale for a photocurrent of10−11A. Stopping potentials for six lines between 3650 and 5770Åare determined by plotting the square root of the photocurrent against retarding potential and by extending the straight portions of these plots to the axis. The slope of a straight line drawn through the stopping potentials, plotted against photon frequency, comes close to the accepted value ofh/e.Perhaps the most instructive aspect of this experiment is the experience with electron and photon energies. The student observes directly that electrons ejected by uv photons are much harder to stop than those ejected by photons of yellow light.

ISSN:0002-9505    

DOI:10.1119/1.1986055

出版商:American Association of Physics Teachers    

年代:1971

数据来源: AIP

摘要:

In this paper, we develop a classical mechanical model for nuclear reactions involving isobaric analog and doorway states. TheRmatrix for the model is identical to the one of the nuclear reaction problem, and the correspondingSmatrix gives rise to such characteristic effects as the Robson enhancement factor for the isobaric resonances.

ISSN:0002-9505    

DOI:10.1119/1.1986056

出版商:American Association of Physics Teachers    

年代:1971

数据来源: AIP