摘要:

Mediaeval optics was dominated by theKitäb-al-manäzurof Ibn al-Haitham. The Latin translation published at Basel in 1572 and known from its Latin title as theOpticae Thesaurusof Alhazen has an interesting woodcut on its title page which is here reproduced.

ISSN:0002-9505    

DOI:10.1119/1.1933640

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

The problem of the potential distribution between two parallel planes at the same potential as a function of the current density passing between the planes is analyzed by successive approximation resulting in power series. The method involves a consideration of the influence of space charge on transit time, and the leading terms of the Maclaurin's series expression for the transit time in powers of the current density are evaluated.

ISSN:0002-9505    

DOI:10.1119/1.1933642

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

A description of a grounded lightning conductor erected in 1754 in Přímětice, Moravia.

ISSN:0002-9505    

DOI:10.1119/1.1933643

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

Nuclear quadrupole resonance is a recently developed branch of radio-frequency spectroscopy which is concerned with magnetic resonance absorption in crystals. This absorption is due to reorientation of the nonspherical atomic nuclei against crystalline electric fields. Related phenomena in isolated molecules are briefly mentioned in the Introduction A. This is followed in Sec. B by an elementary treatment of the electrostatic interaction of a nonspherical nucleus with an axially symmetric inhomogeneous electric field as is found approximately in crystallineCl2, a crystal whose structural units are very nearly undisturbedCl2molecules. Electrostatic torques are shown to exist which cause a precession of the nuclear angular momenta around the molecular axes. As this motion is accompanied by a precession of the magnetic and electric moments of the nuclei, which may interact with alternating electromagnetic fields, this leads over to the transition mechanism between the energy levels which are obtained from the corresponding Hamiltonian. Transition and power absorption phenomena are discussed in more detail in Sec. C. In Sec. D effects are treated which either lead to a broadening of the absorption lines or are connected with the thermal agitation in the crystalline lattice. Some experimental aspects are described and examples of observed absorption lines are given in Sec. E. In the concluding Sec. F all nuclei so far investigated with this method are reviewed in three tables. The nuclear information obtainable from such experiments is pointed out.

ISSN:0002-9505    

DOI:10.1119/1.1933644

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

Maxwell's formulation of electromagnetism is not the only formulation, though it is the most familiar. In particular, the whole subject of electrodynamics can be expressed as an extension of Coulomb's equation, with the magnetic field entirely eliminated. The paper reviews the history of this attack, beginning with the work of Coulomb, Ampère, and Gauss, and concluding with recent developments.

ISSN:0002-9505    

DOI:10.1119/1.1933645

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

The importance of physics to the physician is discussed. It is pointed out that the routine process of physical examination of a patient is, in essence, based on physical principles. A few applications of physics made during every medical student's education are interpreted from the point of view of man as a machine.

ISSN:0002-9505    

DOI:10.1119/1.1933646

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

The flow of water through a capillary from a vessel with vertical walls is shown to simulate the decay of a radioactive sample if the velocity of efflux is low. The rate of flow, when both inertia and viscosity play a part, is worked out under simplifying assumptions.

ISSN:0002-9505    

DOI:10.1119/1.1933647

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

The concept of fictive temperature as a means of describing nonequilibrium states of glass is described. Activation energies and the modern views of chemical rate processes are discussed in relation to the kinetics of the approach of these nonequilibrium states to equilibrium.

ISSN:0002-9505    

DOI:10.1119/1.1933648

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

摘要:

Liquids of three different viscosities have been used in determining the flow permeability of fourteen media composed of spherical glass beads. Darcy's law has been found to hold for a Reynolds number up to 75. Three methods are given for determining the average bead diameters.

ISSN:0002-9505    

DOI:10.1119/1.1933649

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1933650

出版商:American Association of Physics Teachers    

年代:1954

数据来源: AIP