摘要:

It has been shown that when an axially symmetric localized charge distribution carrying a single electric multipole momentQl0is rotated about its symmetry axis, it developes magnetic multipole momentsMl−1,0,Ml+1,0of ordersl−1 andl+1 only. The lower orderl−1 does not contribute forl=0, 1. The resulting magnetic field is a superposition of two pure multipole fields.

ISSN:0002-9505    

DOI:10.1119/1.17042

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

Using Fourier transform and convolution techniques, it is illustrated how all aspects of Fraunhofer diffraction of virtually any aperture real or complex can be calculated and displayed in two‐ and three‐space using an IBM‐compatible PC. Details of program commands using softwarematlabTMare illustrated as well as results of plotting software,surferTM. Fresnel diffraction is illustrated using Fourier transformation.

ISSN:0002-9505    

DOI:10.1119/1.17140

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

A box of massm1rests on a rough plane elevated through an angle φ. The box is connected to a counterweight of massm2by an inextensible rope which passes over an ideal pulley at the higher end of the plane. The box may stick only if μs2≥M2−1, where μsis the coefficient of friction andM≡m2/m1. If, in addition, μs

ISSN:0002-9505    

DOI:10.1119/1.17043

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

Corrected expressions for parameter variances in linear (straight‐line) least‐squares fits given in an earlier paper [B. C. Reed, Am. J. Phys.57, 642–646 (1989)] are presented and discussed. In addition, some simplifications to the solution given in that paper are presented, and some comments made as to the role of weighting.

ISSN:0002-9505    

DOI:10.1119/1.17044

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

Commercially available 3‐cm microwave equipment can produce predictable diffraction patterns if precautions are taken to eliminate standing waves resulting from reflections from various surfaces. Equipment modifications and operating procedures are described for a student laboratory experiment involving single‐slit diffraction in the transition range between Fraunhofer and Fresnel patterns. Polarization measurements are also described.

ISSN:0002-9505    

DOI:10.1119/1.17045

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

Least‐squares fitting is reviewed, in tutorial form, when both variables contain significant errors. Various error models are described; corresponding appropriate weighting is discussed; and the interpretation of weighting is clarified by a physically intuitive description and by graphical results. Resources in the literature on least‐squares fitting that are suitable for physics and astronomy students are reviewed. Algorithms for straight‐line fitting, indicate practical solution methods, are summarized and numerical comparisons are given. Also described are several readily available computer programs that allow fitting for both straight‐line and nonlinear situations and that are appropriate for both research and teaching applications.

ISSN:0002-9505    

DOI:10.1119/1.17046

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

The chaotic motion of the elastic pendulum is studied by means of four indicators, the Poincaré section, the maximum Lyapunov exponent, the correlation function, and the power spectrum. It is shown that for very low and very large energies the motion is regular while it is very irregular for intermediate energies. Analytical considerations and graphical representations concerning the applicability of KAM theorem are also presented. This system and the type of description used are very suitable to introduce undergraduate students to nonlinear dynamics.

ISSN:0002-9505    

DOI:10.1119/1.17047

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

The effect of cyclotron resonance on the detection of microwave radiation by a glow discharge tube has been investigated. This effect was reported about a decade ago for the detection of 70‐GHz millimeter‐wave radiation using a magnetic field of 26 kG. In the present work a similar experiment has been carried out with 9.1‐GHz microwave radiation a resonance in the detection signal at a magnetic field of 3.1 kG has been found. This experiment, which involves the use of an X‐band microwave source, a moderate magnetic field, and the plasma of a simple glow discharge tube, can easily be adopted in a physics student laboratory.

ISSN:0002-9505    

DOI:10.1119/1.17048

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

A simple experiment to determine the complex refractive index of a semiconductor in thin film form through transmittance measurements is presented. The experiment allows us to obtain, from the real part of the refractive index, thendispersive law, and from the imaginary part, the absorption coefficient α. An energy dependence analysis of α is done to obtain the semiconductor band gap value and the nature of the optical transition (direct or indirect). Transmittance data of a CdS thin semiconductor film have been analyzed, and a value for the real part of the refractive index, which is very similar to the bulk value, has been obtained. Also, from the absorption coefficient a band gap value of (2.33±0.02) eV for CdS is deduced, in agreement with previously published values.

ISSN:0002-9505    

DOI:10.1119/1.17049

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.17050

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP