摘要:

An experiment is described in which measurements of time, distance, and speed made in an automobile yield data which can be plotted graphically to clarify motions of displacement, velocity, and acceleration.

ISSN:0002-9505    

DOI:10.1119/1.1934378

出版商:American Association of Physics Teachers    

年代:1957

数据来源: AIP

摘要:

Events and conditions leading to the founding of the Association are recounted here; also some of the objectives and accomplishments of its founders, Dodge and Klopsteg, and of some of its other pioneers, especially Roller and Richtmyer; and some of Richtmyer's statements about the art of teaching physics are quoted with approval.

ISSN:0002-9505    

DOI:10.1119/1.1934379

出版商:American Association of Physics Teachers    

年代:1957

数据来源: AIP

摘要:

A discussion is given of how sets of single, double, and multiple slits may be made for use in lecture demonstrations in physical optics courses where each student has his own set of slits through which a source is viewed with the naked eye. Very careful work is required with very high-grade photographic equipment.

ISSN:0002-9505    

DOI:10.1119/1.1934380

出版商:American Association of Physics Teachers    

年代:1957

数据来源: AIP

摘要:

The electronic potential distribution at the surface of a crystal is described. The periodic potential of the interior is modified at the surface by a redistribution of charge, which may be developed in terms of a number of related dipole double layers, space charge, and net surface charge. The image, exchange, and correlation fields, and the field of the net surface charge are presented. The relationship of these effects to the work function of metals and nonmetals, and their role in rectification in metal-semiconductor contacts is mentioned.

ISSN:0002-9505    

DOI:10.1119/1.1934381

出版商:American Association of Physics Teachers    

年代:1957

数据来源: AIP

摘要:

Frost resulting from cooling of vegetation by nocturnal radiation is a serious agricultural problem. Because of the number of variables involved, attacks on this problem from a purely theoretical point of view have met with only moderate success. It seems logical to suppose that an instrument might be devised which would speed up the natural radiation processes and enable an observer to obtain in a few hours a measure of the cooling which occurs naturally over a period of 12 to 14 hr. Such an instrument could serve as a frost warning device. This paper describes the construction of a radiation device and presents experimental evidence to show that it can be used as a predictor of freezing temperatures at vegetation level.

ISSN:0002-9505    

DOI:10.1119/1.1934382

出版商:American Association of Physics Teachers    

年代:1957

数据来源: AIP

摘要:

A didactical apparatus for the absolute measurement of small coefficients of viscosity (1 centipoise) with an accuracy of 1%is presented. A W-shaped piece rotates about a vertical axis at a variable distance from the walls of an identically shaped vessel, containing the liquid sample. A wire wound on a drum attached to the axis, carries a mass, which accelerates the rotor when falling through a distanceHin the time intervalT. When completely unrolled the wire is rewound on the drum and the mass is lifted up to a smaller heightH′in a shorter timeT′. The determination of both distances and time intervals permits calculation of the coefficient of viscosity.

ISSN:0002-9505    

DOI:10.1119/1.1934383

出版商:American Association of Physics Teachers    

年代:1957

数据来源: AIP

摘要:

A didactical apparatus for accurate determination of resonance curves is presented. A bifilarly suspended disk, whose natural period is variable between large limits while the system is oscillating, is suited for easy determination of a resonance curve, because the period of the forced oscillation can remain unchanged during operation. The rigidity and hence the natural period of the pendulum is altered by a change in the mass supported by the bifilar suspension; this is done by means of a third axial wire, from the disk to a yoke carrying counterweights.

ISSN:0002-9505    

DOI:10.1119/1.1934384

出版商:American Association of Physics Teachers    

年代:1957

数据来源: AIP

摘要:

Jensen's recently published Chladni figures can be interpreted as normal modes of vibration with antinodal centers which are distorted by the experimental method employed to produce them. Thefreetransverse vibrations of uniform plates always conform with the symmetry of the geometrical surfaces. The principle of symmetry and of corresponding vibrations enables them to be identified and arranged in a systematic manner. The solid carbon dioxide method of exciting free vibrations, supplemented by the bow, produces the most symmetrical figures.

ISSN:0002-9505    

DOI:10.1119/1.1934385

出版商:American Association of Physics Teachers    

年代:1957

数据来源: AIP

摘要:

The quantitative usefulness of an inexpensive chamber particularly adaptable for small colleges is shown. In particular, the beta spectrum of Pm-147 was obtained and compared with the spectrum which had been obtained by the use of an intermediate-image type spectrometer. The end-point energy as obtained here is 231 kev for a difference of 3.5% as compared with published values of 223 kev.

ISSN:0002-9505    

DOI:10.1119/1.1934386

出版商:American Association of Physics Teachers    

年代:1957

数据来源: AIP

摘要:

Proportional counters suitable for demonstration purposes are described, and some experiments to illustrate counter operation are discussed. The charge carried by the positive ions produced in the multiplication process, and the localization of the avalanche, is revealed in a special proportional counter whose cathode is covered by a layer of polythene. Other properties of this type of counter, such as its ability to work for a considerable period of time without a high-voltage supply, are pointed out.

ISSN:0002-9505    

DOI:10.1119/1.1934387

出版商:American Association of Physics Teachers    

年代:1957

数据来源: AIP