摘要:

The history of the photoelectric effect is described. An analysis that field quantization is not required for an explaination of the photoelectric effiect is also given. (AIP)

ISSN:0002-9505    

DOI:10.1119/1.18494

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18794

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18495

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

Early in his career Robert Millikan experimented with a laboratory-based method of teaching introductory physics that bears close resemblance to Workshop Physics.®In this talk, key elements of Workshop Physics are summarized. Some Workshop Physics activities are described which involve apparati that are used for rapid observations of conceptual aspects of physical phenomena as well as for equation verification experiments. Challenges are discussed that must be faced if recently developed activity-based approaches to teaching based on the outcomes of physics education research are to provide a foundation for a major paradigm shift in physics teaching.

ISSN:0002-9505    

DOI:10.1119/1.18496

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

A beam of electromagnetic waves, produced by a “ham” transmitter at a frequency just below 450 MHz, is studied using a pair of antennas, one an electric and the other a magnetic “dipole,” each coupled to subminiature lamp bulb. These bulbs become very brightly lit in response to the local time average values of |E|2and |B|2, respectively. Most strikingly, the interleaving of the electric and magnetic oscillation maxima in a standing wave is seen. This and other aspects of the phenomena are described using an accompanying pedagogical approach which emphasizes the primary idea of wave superposition.

ISSN:0002-9505    

DOI:10.1119/1.18497

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

The basic notions of statistical mechanics (microstates, multiplicities) are quite simple, but understanding how the second law arises from these ideas requires working with cumbersomely large numbers. To avoid getting bogged down in mathematics, one can compute multiplicities numerically for a simple model system such as an Einstein solid—a collection of identical quantum harmonic oscillators. A computer spreadsheet program or comparable software can compute the required combinatoric functions for systems containing a few hundred oscillators and units of energy. When two such systems can exchange energy, one immediately sees that some configurations are overwhelmingly more probable than others. Graphs of entropy vs. energy for the two systems can be used to motivate the theoretical definition of temperature,T=(∂S/∂U)−1, thus bridging the gap between the classical and statistical approaches to entropy. Further spreadsheet exercises can be used to compute the heat capacity of an Einstein solid, study the Boltzmann distribution, and explore the properties of a two-state paramagnetic system.

ISSN:0002-9505    

DOI:10.1119/1.18490

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

This paper presents a recently discovered and newly translated manuscript of a lecture by Heinrich Rudolf Hertz, long famous for his 1888 discovery of long-wavelength electromagnetic waves. Hertz delivered this address on 20 April 1885 as his inaugural lecture to the faculty at the Technische Hochschule in Karlsruhe (now the Universität Karlsruhe), where he was to make his most important contributions to physics. Although written over 110 years ago, this historical document records both Hertz’s insightful view of the Earth’s energy situation at that time and his remarkably good order-of-magnitude estimates of the energy sources then known to be available to the Earth.

ISSN:0002-9505    

DOI:10.1119/1.18565

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

One hour active-engagement tutorials using microcomputer-based laboratory (MBL) equipment were substituted for traditional problem-solving recitations in introductory calculus-based mechanics classes for engineering students at the University of Maryland. The results of two specific tutorials, one on the concept of instantaneous velocity and one on Newton’s third law were probed by using standard multiple-choice questions and a free-response final exam question. A comparison of the results of 11 lecture classes taught by six different teachers with and without tutorials shows that the MBL tutorials resulted in a significant improvement compared to the traditional recitations when measured by carefully designed multiple-choice problems. The free-response question showed that, although the tutorial students did somewhat better in recognizing and applying the concepts, there is still room for improvement.

ISSN:0002-9505    

DOI:10.1119/1.18498

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

The contribution of the electromagnetic self-field to the energy and momentum of a charge and/or current carrying body is considered within classical physics and discussed in simple terms using nontrivial exactly solvable examples. The Lorentz-transformation properties of the energy and momentum of the body can be maintained by taking into account the relativistic effects of the mechanical stresses due the sources of the self-field, or by separating the energy and momentum of a moving self-field from those of a nonelectromagnetic origin in a relativistically covariant way. In either procedure, a proper account must be taken of the hidden mechanical momentum that, in general, is contained in a stationary body that carries both charge and current, and which is equal and opposite to the momentum of the static electromagnetic self-field. Hidden momentum and the momentum of a static electromagnetic field are indispensable concepts of direct physical significance in classical electrodynamics.

ISSN:0002-9505    

DOI:10.1119/1.18789

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

We present a new description of linear Landau damping of plasma waves. The process is found to be governed by a set of two equations with an energy conservation law that is different from the standard form. An analytical solution containing an explicit expression for the velocity distribution function is given. The effect of different initial conditions is demonstrated numerically. We argue that our new approach has several advantages as compared with the standard presentations of introductory plasma textbooks.

ISSN:0002-9505    

DOI:10.1119/1.18521

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP