摘要:

We discuss the ‘‘images’’ formed when the light from a distant source suffers a large deflection in the intense gravitational field in the immediate vicinity of a Schwarzschild black hole. The light can circle around the black hole one or several times, and therefore give rise to a sequence of images. We show that the deflection angles and the intensities of the images can be expressed in terms of elliptic integrals, leading to simple approximations in the limiting case of very large deflection angles.

ISSN:0002-9505    

DOI:10.1119/1.15126

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

The actual range, flight time, and maximum height of an ICBM are compared to the predictions of five simple approximations that are more sophisticated than the standard flat‐Earth‐with‐constant‐gravity problem but more elementary than the full Keplerian solution. The simplest of these approximations is accessible to first‐year students and gives results in closed form whose range predictions are in good agreement with the Keplerian ranges at typical ICBM speeds.

ISSN:0002-9505    

DOI:10.1119/1.15127

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

A common, everyday phenomenon has a geometrical aspect that, in some respects, is analogous to a second‐order phase transition. Concepts such as spontaneous symmetry breaking, order parameter, critical point, and critical exponent can thus be exhibited in a purely geometrical context. The purpose of the model, which is entirely pedagogical, is to illustrate in an elementary and amusing way some of the concepts associated with phase transition theory.

ISSN:0002-9505    

DOI:10.1119/1.15128

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

An analysis of the conceptual structure of physics identifies essential factual and procedural knowledge which is not explicitly formulated and taught in physics courses. It leads to the conclusion that mathematical modeling of the physical world should be the central theme of physics instruction. There are reasons to believe that traditional methods for teaching physics are inefficient and substantial improvements in instruction can be achieved by a vigorous program of pedagogical research and development.

ISSN:0002-9505    

DOI:10.1119/1.15129

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

Modeling theory was used in the design of a method to teach problem solving in introductory mechanics. A pedagogical experiment to evaluate the effectiveness of the method found positive results.

ISSN:0002-9505    

DOI:10.1119/1.15130

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

The energy bands of electrons in a one‐dimensional periodic potential consisting of two different rectangular barriers and wells per period are calculated. The variation of the energy band structure as a function of the size of the wells in each period is presented. The results can be used to obtain the energy scheme of a superlattice with the layer structure of this model. The method used can be applied to solve for the band structure of an electron in a periodic potential consisting of multiple barriers per period.

ISSN:0002-9505    

DOI:10.1119/1.15131

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

We calculate the polarization of the quantum and classical electrons confined in a one‐dimensional infinite potential well in the presence of a static electric field. As the external field is increased, the polarization always increases for a quantum electron in the ground state, but the polarization of an electron in any excited state decreases for a weak field and increases after passing a minimum. The polarization of a classical electron with nonzero initial kinetic energy is similar to the response of a quantum electron in excited states. The polarization determined by the diffusion equation is similar to the polarization of a quantum electron in the ground state.

ISSN:0002-9505    

DOI:10.1119/1.15132

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15133

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15134

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15135

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP