ISSN:0002-9505    

DOI:10.1119/1.16950

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16952

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

The PSSC teaching film, ‘‘Frames of Reference,’’ was made in 1960, and was one of the first audio‐visual attempts at showing how your physical ‘‘point of view,’’ or frame of reference, necessarily alters both your perceptions and your observations of motion. The gentle humor and original demonstrations made a lasting impact on many audiences, and with its recent re‐release as part of the AAPT Cinema Classics videodisc it is timely that we should review both the message and the methods of the film. An annotated script and photographs from the film are presented, followed by extension material on rotating frames which teachers may find appropriate for use in their classrooms: constructions, demonstrations, an example, and theory.    

ISSN:0002-9505    

DOI:10.1119/1.16953

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

This elementary review paper presents the compelling evidence which supports the notion that quantum mechanics is much too simple a theory to adequately describe a complex world. Rigorous arguments based on algorithmic complexity theory are used to show that both the quantum Arnol’d cat and a broad category of finite, bounded, undriven, quantum systems do not obey the correspondence principle, implying that quantum mechanics is also not complete. An experiment, well within current laboratory capability, is proposed which can expose the inability of quantum mechanics to adequately describe macroscopic chaos. In its final section, this paper describes a theoretical framework that provides a proper setting for interpreting these surprising results.

ISSN:0002-9505    

DOI:10.1119/1.16954

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

Detailed instructions for the construction and operation of a diode laser system with optical feedback are presented. This system uses feedback from a diffraction grating to provide a narrow‐band continuously tuneable source of light at red or near‐IR wavelengths. These instructions include machine drawings for the parts to be constructed, electronic circuit diagrams, and prices and vendors of the items to be purchased. It is also explained how to align the system and how to use it to observe saturated absorption spectra of atomic cesium or rubidium.

ISSN:0002-9505    

DOI:10.1119/1.16955

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

There has recently been a revival of an old controversy over whether Ampere’s original law of force between current elements is to be preferred over the more familiar and universally used Biot–Savart–Lorentz law. Although it is agreed that the two laws give identical results when used to calculate the force between two circuits, it has been claimed that if Ampere’s law is applied to the action of a circuit upon part of itself it predicts internal longitudinal forces that are excluded by Biot–Savart–Lorentz. The existence of longitudinal forces has been inferred from observations of the buckling of the rails in a railgun, attributed to compressive stress, and the fracture of long wires subjected to pulsed currents, attributed to ‘‘Ampere tension.’’ An experiment has been performed that should provide an unambiguous demonstration of this longitudinal force, if it exists. The apparatus consisted of a rigid coaxial circuit in which an unsymmetrical section of the center conductor was free to move in the axial direction under the influence of the longitudinal force. Pulsed currents of up to 100 kA were passed through the circuit but no evidence of a longitudinal force was found. It is shown that this result is consistent with Ampere’s force law, and that claims that the law predicts longitudinal forces are based on the incomplete application of the law.

ISSN:0002-9505    

DOI:10.1119/1.16956

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

The group velocity of any wave transforms under Lorentz boosts as a particle velocity, and so by the Einstein velocity addition relations. This is expected for the velocity of energy transport in spite of the presence of a medium and so a preferred frame. The phase velocity has the same transformation property only when the group and phase velocities are parallel and the product of their magnitudes is equal toc2. A proof is given of the relativistic group velocity transformation which is simple and novel, and which uses spatial filtering concepts to derive the formula for group aberration as a consequence of that for phase aberration. This gives some physical insight into the previous proofs based on a four‐vector analysis.

ISSN:0002-9505    

DOI:10.1119/1.16957

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

An exactly soluble fermionic system (anharmonic oscillator) is presented. Exact expressions for average quantities such as the number of particles, energy, and magnetization of an ensemble of quantum systems in equilibrium with a reservoir of particles and heat are derived. Critical curves of the average magnetization as a function of temperature are obtained for a lattice of interacting anharmonic oscillators within the mean field approximation. To clarify the role played by the parameters of the present model, the Ising model is studied as a limiting case.  

ISSN:0002-9505    

DOI:10.1119/1.16958

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

The formalism of functional integration in the holomorphic representation is illustrated by calculating the partition function for the small polaron Hamiltonian in the atomic limit. As an introduction, the standard construction of the functional integral representation of the partition function for a coupled fermion‐boson system is reviewed.

ISSN:0002-9505    

DOI:10.1119/1.16959

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

It is pointed out that for the class of potentialsV(x)=A‖x‖n, the quantum‐mechanical virial theorem 〈φm‖T‖φm〉=(n/2)〈φm‖V‖φm〉 is in fact valid for any multiparameter trial wave function ψt=(1/√b)φt(x/b,a0̄,a1̄,...ar̄), wherea0̄,a1̄,...ar̄, are dimensionless parameters, providedbis chosen to minimize 〈ψt‖T+V‖ψt〉, i.e., one requires (∂/∂b)[〈ψt‖T+V‖ψt〉]=0. A particular trial wave function of this type is used to illustrate this result.

ISSN:0002-9505    

DOI:10.1119/1.16960

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP