摘要:

The statistics of a radioactive chain composed of father nuclei decaying into two daughter nuclei is analyzed. To illustrate the usefulness of generating functions, a master equation is used for the probability density and then an equation is derived and solved for the corresponding generating function. From this function the time evolution of the probability density is obtained. Two cases are considered: (1) when an external source gives rise to the father nuclei and (2) with no external source present. The effect of different initial conditions is also analyzed. The results clarify some misleading statements appearing in the literature, and provide teachers with interesting examples of the use of generating functions.

ISSN:0002-9505    

DOI:10.1119/1.16348

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

When a photon is transmitted from a sourceSthrough a uniform gravitational field for which the acceleration due to gravity isgto a detectorDlocated a distancehaboveS, the frequency νDof the photon measured at the detector is less than the frequency νSmeasured at the source. The various assumptions and approximations employed in textbook analyses of this phenomenon are considered. The exact dependence of νDon νS,g, andhis then determined first on the conventional assumption that the frequency shift in a uniform gravitational field is the same as the frequency shift in a uniformly accelerating reference frame in field‐free space and, second, on the more valid assumption that space‐time is curved in a uniform gravitational field and the frequency shift in the field is a consequence of the space‐time curvature. The expressions obtained depend not only on which of the above assumptions is made but also on the exact interpretation of the quantitiesgandh.

ISSN:0002-9505    

DOI:10.1119/1.16349

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

Microcomputer‐based laboratory (MBL) tools have been developed which interface to Apple II and Macintosh computers. Students use these tools to collect physical data that are graphed in real time and then can be manipulated and analyzed. The MBL tools have made possible discovery‐based laboratory curricula that embody results from educational research. These curricula allow students to take an active role in their learning and encourage them to construct physical knowledge from observation of the physical world. The curricula encourage collaborative learning by taking advantage of the fact that MBL tools present data in an immediately understandable graphical form. This article describes one of the tools—the motion detector (hardware and software)—and the kinematics curriculum. The effectiveness of this curriculum compared to traditional college and university methods for helping students learn basic kinematics concepts has been evaluated by pre‐ and post‐testing and by observation. There is strong evidence for significantly improved learning and retention by students who used the MBL materials, compared to those taught in lecture.

ISSN:0002-9505    

DOI:10.1119/1.16350

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

The formulations of Newton’s law of inertia in university‐level textbooks usually follow the Motte–Cajori translation of Newton’sPrincipia. The rich content of Newton’s law of inertia as a causality principle for mechanics is partly hidden by Motte’s mistranslation of the Latin phrasenisiquatenusasunlessinstead ofexceptinsofaras. One effect of this error is a tendency to isolate from the law some of the ‘‘Definitions’’ that precede Newton’s statement of the three laws of motion. These definitions, when taken together with the laws, provide the basis for Newton’s quantitative and qualitative elaboration of the coupled concepts of mass and force.

ISSN:0002-9505    

DOI:10.1119/1.16351

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

Two experiments, suitable for a 3‐h undergraduate laboratory period, employing optical fibers as position sensors are described. These two experiments are based on microbending losses in the fiber and on an external moving reflector, respectively. For each case a model that characterizes the behavior of the transmitted light output from the sensor is given. A knowledge of the model and subsequent analysis for each sensor provide natural experiments suitable for an undergraduate physics/optics laboratory.

ISSN:0002-9505    

DOI:10.1119/1.16352

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

A strain gauge is employed to determine the coefficient of thermal expansion of a solid. The apparatus is interfaced to a computer to obtain a linear plot of displacement against temperature.

ISSN:0002-9505    

DOI:10.1119/1.16353

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

The principle and the construction of an intensity and a frequency‐stabilized single‐mode internal mirror He–Ne 633‐nm laser are described. An intensity stability better than 10−3and a frequency stability better than 10−8are obtained. The design is very simple, and the system is recommended for student laboratories and for laser‐wavelength meters.

ISSN:0002-9505    

DOI:10.1119/1.16354

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16339

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16340

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16342

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP