ISSN:0002-9505    

DOI:10.1119/1.12685

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

The author has selected resource material that focusses on black holes.

ISSN:0002-9505    

DOI:10.1119/1.12686

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

An elementary formalism for representing curved space‐time is developed which allows transparent qualitative explanation of such general relativistic effects as gravitational redshift, deflection of starlight, and precession of a gyroscope in orbit. The formalism is based on a method of surveying and subsequent mapmaking and does not rely on the usual tensor machinery, connection coefficients, etc. Yet metric (survey) information can be quantitatively specified and subsequently used to calculate the magnitudes of those relativistic effects and even to build a simple computer simulation. In addition, the formalism is used to make a conceptual analysis of Einstein’s principle of equivalence which explains the famous factor of two missing from his first calculation of the deflection of starlight using only the equivalence principle. A final section outlines a number of student activities.

ISSN:0002-9505    

DOI:10.1119/1.12687

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

The magnitude of the proper acceleration of a static observer (or test particle) in a static, isolated, spherically symmetric space‐time region is compared with the Newtonian result including the situation in the interior of a perfect‐fluid star. The calculation shows that the proper acceleration diverges on the event horizon of a spherically symmetric black hole. The ’surface gravity’ of a spherically symmetric black hole, as used in descriptions of the Hawking radiation, is then explicitly related to the accelerations of such static observers, thus providing a simple physical interpretation of the surface gravity and illustrating the global (nonlocal) nature of the event horizon. The calculations are presented in the SI physical equations used almost exclusively by many students and teachers of physics.

ISSN:0002-9505    

DOI:10.1119/1.12688

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

The Two Cultures schism is a persistent problem in our society. For over a century, scientific spokesmen and literary critics, from T. H. Huxley and M. Arnold to C. P. Snow and F. R. Leavis, have been involved in the Two Cultures issue. This article examines the evolution of the controversy between the ’’scientific’’ and ’’humanistic’’ elements of Western culture and its relation to educational policies. The division and antagonism between these two cultures appears to have arisen from differences in the human attitudes that they are preceived to engender. ’’Scientific’’ professionalism has been associated with a progressive optimism and self‐assurance that nurture a broad humanitarianism, while the ’’literary’’ tradition is characterized by restraint, acceptance, and a more selective humanism.

ISSN:0002-9505    

DOI:10.1119/1.12689

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

When the energy of the electrons in a beam is determined by noting the value of a stopping potential that cuts off the beam, the current density of the beam must be below a limiting value determined by space charge considerations. Above this limit, cutoff occurs sharply at a voltage that may be far below the potential that accelerates the beam. At stopping potentials above cutoff, a weak tail of current does persist all the way up to the full potential of the beam.

ISSN:0002-9505    

DOI:10.1119/1.12690

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

Bohr quantization of circular orbits is modified by the addition of radial excitations treated in the harmonic approximation, and by the use of half‐interger angular momentum quantum numbers. Applied to the hydrogen spectrum, the modification leads to a correct assignment of angular momenta, but fails to reproduce the ground state. Applied to charmonium this simple method yields a spectrum in fairly good agreement with the results of other more complicated calculations.

ISSN:0002-9505    

DOI:10.1119/1.12691

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

Dirac’s extensible model of the electron is presented on an elementary level retaining the basic physical idea.

ISSN:0002-9505    

DOI:10.1119/1.12692

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

Appropriate partition functions for the van der Waals gas and the nuclear paramagnetic system are used to obtain the entropy expressions and the equations of state. The particular form for each of the four Maxwell’s relations is evaluated for these two systems, establishing internal consistency with the first two laws of thermodynamics. The well‐known limiting expressions for the ideal gas and Curie law paramagnetism readily follow. Maxwell’s relations are important in analyzing the throttling process for a nonideal gas and adiabatic demagnetization for a nuclear spin system. The van der Waals equations are of classical orgin, they have a limited temperature range of validity, and they do not describe real gases at low temperature after they have condensed. The low‐temperature predictions of the equations describing the nuclear paramagnetic system are consistent with the third law of thermodynamics because the partition function takes quantum effects into account.

ISSN:0002-9505    

DOI:10.1119/1.12693

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

Using a solar cell as a sensor, a low‐cost instrument can be constructed which measures both the instantaneous and integrated value of solar flux. The process of constructing and calibrating the instrument constitutes an excellent undergraduate experimental project, affording the student an opportunity to examine a variety of aspects associated with solar energy measurements.

ISSN:0002-9505    

DOI:10.1119/1.12694

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP