ISSN:0002-9505    

DOI:10.1119/1.11921

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

It is shown that perspective distortion in photography can be explained analytically if the eye operates as a simple lens and the brain remembers the hyperbolic relationship between image size and distance.

ISSN:0002-9505    

DOI:10.1119/1.11922

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

The problem of deriving accurate long‐wavelength approximations of a particular dispersion equation for electromagnetic waves in a magnetized plasma is examined. Because the dispersion equation includes dependence upon external parameters, the approximation obtained by straightforward expansion is invalid in certain cases. An accurate approximation is derived in these cases by a modified expansion technique. Although only one specific practical problem is studied here, this example involves and exhibits general techniques that have broad application in related problems. Some features of long‐wavelength low‐frequency waves in a magnetized high‐temperature plasma are illustrated.

ISSN:0002-9505    

DOI:10.1119/1.11923

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

By dealing with the Schrödinger equation for a free particle in the coordinate representation alone, the expression for ψ (r,t) at timetis derived in terms of ψ (r,t0) at an initial instantt0with the use of the ’’method of self‐similar solution of partial differential equations.’’ The use of Green’s function is necessary due to the complex nature of the Schrödinger equation. The same technique can also be applied to the case of spreading of wave packets in a dissipative medium.

ISSN:0002-9505    

DOI:10.1119/1.11924

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

Solutions to linear wave equations can always be expressed as a superposition of special solutions called plane waves. Some solutions to an important class of nonlinear wave equations can be thought of as a superposition of special solutions called solitons. In this paper, we present a simple method for generating these special soliton solutions.

ISSN:0002-9505    

DOI:10.1119/1.11925

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

Amorphous tungsten trioxide films offer an interesting electrochromic system whose properties are readily amenable to study in a senior undergraduate laboratory. Basic optical color center properties, and electron and proton diffusion processes are characterized for the HxWO3produced; additional experiments including the variation of the chemical potential of the hydrogen component and low‐temperature exploration of the metal‐insulator transition are proposed for the advanced student. The samples are easily prepared and measured by elementary means. The broad solid‐state concepts involved enrich standard advanced laboratory repertoires of more conventional nuclear and NMR experiments.

ISSN:0002-9505    

DOI:10.1119/1.11926

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

The complete discharge of a capacitor through a real resistor is limited by thermal noise. A meaningful discharge timetdis defined by equating the charge across the capacitor in a noiselessRCcircuit to the rms charge fluctuation in a noisy circuitQ0(td) =[〈 (δQ)2〉t]1/2. Three derivations are reviewed for the well‐known result 〈 (δQ)2〉t=kTC. One derivation shows explicitly that δQ(t) can be determined with the noise currentin(t) as its source. Several examples of potential interest in the classroom are discussed.

ISSN:0002-9505    

DOI:10.1119/1.11927

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

A course in modern physics and Eastern mystical philosophy is described.

ISSN:0002-9505    

DOI:10.1119/1.11928

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

Sixty students in a second semester freshman physics class were administered a test of formal operational reasoning. The composite logical test score was correlated with students’ final examination grades and yielded a correlation of 0.49. Furthermore, the composite correlation distribution provided evidence that the ability to employ formal operational reasoning is a necessary, though not sufficient, condition for student success in physics. These results point to the importance of seriously considering including, within the framework of physics courses, interactions and experiences designed to develop logical reasoning.

ISSN:0002-9505    

DOI:10.1119/1.11929

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP

摘要:

Closed formulas for the Coulomb and exchange integrals in the excited states 1snl,l=n−1, of the two‐electron atom are applied to the computation of the ionization energy of the singlet and tripet 1s2pstates from He iup to O viiand to singlet and triplet 1s3dand 1s4fstates of He iand Li ii. Two methods are compared: (a) the use of first‐order perturbation theory considering the mutual electrrostatic repulsione2/r12as a small perturbation and (b) imposing as solution of the Schrödinger equation a symmetrized product of aZand a screenedZ−1 hydrogenic wave functions. Computed and experimental values of the ionization energy and of the singlet‐triplet interval are compared and the evolution of agreement with increasingZandnis discussed.

ISSN:0002-9505    

DOI:10.1119/1.11930

出版商:American Association of Physics Teachers    

年代:1979

数据来源: AIP