摘要:

Caricatures of famous scientists, particularly when done by competent artists, often have historical as well as entertainment value. Two amusing caricatures of Isaac Newton, one by John Leech, the other by George Cruikshank, are here reproduced primarily for the reader's entertainment.

ISSN:0002-9505    

DOI:10.1119/1.1933710

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

The transfer of momentum between a conduction electron and a crystal lattice is examined in detail. By physical considerations we are led to the expression(mm*)ij = δij+∑GGiδδkj|aG(k)|2for the reciprocal effective mass tensor, whereGis2πtimes a reciprocal lattice vector andaG(k)is a coefficient in the momentum representation of the Bloch eigenfunction:ψk = ∑GaG(k) exp[i(G+k)·r]. This expression for the effective mass tensor is shown to be completely equivalent to the usual definition.

ISSN:0002-9505    

DOI:10.1119/1.1933711

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

A method to analyze the experimental data is suggested, in which no assumption is made beforehand that the motion is uniformly accelerated. Instantaneous velocities are obtained from the limits approached by the average velocities, and the linearity of velocityvstime curve proves the constancy of the acceleration.

ISSN:0002-9505    

DOI:10.1119/1.1933712

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

The nature of the binding in molecular and ionic crystals and in metals is briefly discussed from an intuitive point of view. The salient features of the Slater-Pauling theory of the valence bond are then developed by generalizing the results of the Heitler-London treatment of the hydrogen molecule. The application of the theory to the calculation of the cohesive energy of diamond, the classic example of a valence crystal, is then discussed.

ISSN:0002-9505    

DOI:10.1119/1.1933713

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

A brief review is given of the advances which have been made in the field of neutron diffraction during the past several years. The experimental techniques that have been developed are discussed, and illustrations are cited of several fields of application where information is obtained which would be very difficult or impossible to obtain by x-ray or electron diffraction.

ISSN:0002-9505    

DOI:10.1119/1.1933715

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

The significant aspects of photonuclear processes are reviewed in terms of the trends in research since their discovery in 1934. Experimental techniques with high-energy x-radiation, which are currently employed in these investigations, are described.

ISSN:0002-9505    

DOI:10.1119/1.1933716

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

The theoretical basis and the historical background of five systems of units are described: the British gravitational system, the British absolute system, the metric absolute (cgs) system, the metric gravitational system, and the mks system. No one system is considered superior to any other, for each one has its advantages and its usefulness. It is shown that a law of physics can have exactly the same form in each of the five systems, but common practices are described in which this principle is not maintained. It is suggested that a student needs to see the complete picture of the systems, and that this should be presented as early in the physics curriculum as possible.

ISSN:0002-9505    

DOI:10.1119/1.1933717

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

The Maxwell relation,curlB = (μk/c)δE/δt+4πμj, is obtained directly by differentiation without mention of displacement current. It is also deduced as a consequence of propagation with speedc, and the form of the expressions chosen for the fieldsEandH. These methods of examining retarded action of charge on charge have the advantage over emphasis on continuous fields that weaknesses of classical theory become evident, and closer correlation with symmetric propagation theories becomes possible.

ISSN:0002-9505    

DOI:10.1119/1.1933718

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

Attention is called to the importance of an experimental study of the laws of light absorption in the intermediate and advanced physics laboratory. A simple arrangement is described for measuring the absorption coefficients of solids and liquids, and suggestions are made for various experiments with commercial apparatus.

ISSN:0002-9505    

DOI:10.1119/1.1933719

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

Effects of radiation in producing color changes, often called solarization, in glass are described, in close analogy with modern work onFcenters especially in alkali-halide crystals. Photosensitive glasses in which the action of radiation is to produce centers of nucleation around which colloidal or crystalline precipitates can form are also discussed.

ISSN:0002-9505    

DOI:10.1119/1.1933721

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP