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Dec 2009

Volume 77, Issue 12, pp. 1093-I17

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AJP Reviewers

Jan Tobochnik, Editor and Harvey Gould, Associate Editor

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1093

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Below is a list of 898 individuals who have reviewed manuscripts for the American Journal of Physics from September 1, 2008 to August 31, 2009. If you reviewed for AJP during this time and are not on the list, we apologize and hope that you will let us know so that we can correct our records. The thoughtful and expert advice provided by our reviewers is essential for maintaining the quality of the journal and insuring that it fulfills its educational mission. On behalf of all AJP authors and readers, we thank all who have served as reviewers.
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01.10.-m Announcements, news, and organizational activities
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A water wave analog of the Casimir effect

Bruce C. Denardo, Joshua J. Puda, and Andrés Larraza

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1095

Online Publication Date: Nov 2009

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Two rigid plates are vertically suspended by thread such that they are parallel to and opposite each other. The plates are partially submerged in a dish of liquid that is attached to the top of a vertical shake table. When the shake table is driven with noise in a frequency band, random surface waves are parametrically excited, and the plates move toward each other. The reason for this attraction is that the waves carry momentum, and the wave motion between the plates is visibly reduced. The behavior is analogous to the Casimir effect, in which two conducting uncharged parallel plates attract each other due to the zero-point spectrum of electromagnetic radiation. The water wave analog can be readily demonstrated and offers a visual demonstration of a Casimir-type effect. Measurements of the force agree with the water wave theory even at large wave amplitudes, where the theory is expected to break down. The water wave analog applies to side-by-side ships in a rough sea and is distinct from the significant attraction that can be caused by a strong swell.
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01.50.Pa Laboratory experiments and apparatus
47.00.00 Fluid dynamics

On thermionic emission and the use of vacuum tubes in the advanced physics laboratory

Paul J. Angiolillo

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1102 | Cited 3 times

Online Publication Date: Nov 2009

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Two methods are outlined for measuring the charge-to-mass ratio e/me of the electron using thermionic emission as exploited in vacuum tube technology. One method employs the notion of the space charge in the vacuum tube diode as described by the Child–Langmuir equation; the other method uses the electron trajectories in vacuum tube pentodes with cylindrical electrodes under conditions of orthogonally related electric and magnetic fields (the Hull magnetron method). The vacuum diode method gave e/me=1.782±0.166×10+11 C/kg (averaged over the vacuum diodes studied), and the Hull magnetron method gave e/me=1.779±0.208×10+11 C/kg (averaged over both pentodes and the anode voltages studied). These methods afford opportunities for students to determine the e/me ratio without using the Bainbridge tube method and to become familiar with phenomena not normally covered in a typical experimental methods curriculum.
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01.50.Pa Laboratory experiments and apparatus

Quantitative analysis of the electric dipole on finite sized graphite sheets

David Groh

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1107

Online Publication Date: Nov 2009

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Graphite sheets are commonly used in introductory physics laboratories to model electric potential patterns for systems such as dipoles and parallel plates. Usually, silvered ink pens are used to draw patterns on the sheets and appropriate voltages are then applied. Quantitative experiments are often done at the intermediate level. Students are often puzzled by the failure of the patterns to confirm to the theoretical figure in the manual that came with the kit. I discuss measuring difficulties and some of the common theoretical methods for analyzing edge effects on the sheets.
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01.50.Pa Laboratory experiments and apparatus
41.00.00 Electromagnetism; electron and ion optics

A student’s guide to searching the literature using online databases

Casey W. Miller, Michelle D. Chabot, and Troy C. Messina

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1112 | Cited 2 times

Online Publication Date: Nov 2009

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A method is described to empower students to efficiently perform general and specific literature searches using online resources. The method was tested on undergraduate and graduate students with varying backgrounds in scientific literature. Students involved in this study showed marked improvement in their awareness of how and where to find accurate scientific information.
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01.30.-y Physics literature and publications

Learning of content knowledge and development of scientific reasoning ability: A cross culture comparison

Lei Bao, Kai Fang, Tianfang Cai, Jing Wang, Lijia Yang, Lili Cui, Jing Han, Lin Ding, and Ying Luo

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1118 | Cited 1 time

Online Publication Date: Nov 2009

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We report the results of our study of the connections between students’ learning of physics content knowledge and the development of general scientific reasoning abilities. In particular, we seek to determine whether and to what extent content learning affects the development of general reasoning abilities. Pre-college-instruction data of first-year college students in the United States and China were collected using the FCI, BEMA, and Lawson’s classroom test of scientific reasoning. We find that the rigorous learning of physics knowledge in middle and high schools has made a significant impact on the ability of students in China to solve physics problems, but this knowledge does not seem to have a direct effect on their general scientific reasoning ability, which is determined to be at the same level as that of the students in the United States.
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01.40.Fk Research in physics education

Spreadsheet physics: Examples in meteorology and planetary science

Rhett Herman

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1124

Online Publication Date: Nov 2009

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By utilizing the iterative capabilities of spreadsheets, students who do not have a programming background may obtain numerical solutions to complex equations. This paper discusses two examples of spreadsheet programming. One models the structure of a planet using a set of ordinary differential equations depending on the radius of the planet. The other involves coupled partial differential equations in a model of a planetary atmosphere. The results of the planetary models are compared to the values for Earth and Neptune. The results of the atmospheric model are compared to values for Earth’s atmosphere.
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02.70.-c Computational techniques; simulations
92.00.00 Hydrospheric and atmospheric geophysics

Raman scattering of carbon disulfide: The temperature effect

Dake Wang, Kathryn Mittauer, and Nicholas Reynolds

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1130 | Cited 1 time

Online Publication Date: Nov 2009

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A low-cost Raman system was constructed and used to perform Raman scattering measurements on liquid carbon disulfide at different sample temperatures. The ν1 and ν3 bands are identified based on the frequencies calculated by the normal mode analysis. The ratio of the intensities of the anti-Stokes and Stokes bands can be used to illustrate the Boltzmann distribution of the molecules among the vibrational energy levels.
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01.50.Pa Laboratory experiments and apparatus
30.00.00 ATOMIC AND MOLECULAR PHYSICS

Interference with polarized light beams: Generation of spatially varying polarization

B. M. Rodríguez-Lara and I. Ricardez-Vargas

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1135

Online Publication Date: Nov 2009

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We propose a method based on a Mach–Zehnder interferometer to analyze the superposition of polarized laser beams at a given angle. The focus of our study is the spatially varying polarization state of the resulting field, also known as a polarization grating, generated by this setup. Our proposal combines a description of the resulting field in terms of its Stokes parameters with an experimental demonstration of the existence of such a polarization grating due to the effects of polarization on beam interference experiments.
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01.50.Pa Laboratory experiments and apparatus
42.00.00 Optics

Rotational states of a benzenelike ring and Bloch’s theorem

Y. C. Lee and Wei Z. Lee

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1144

Online Publication Date: Nov 2009

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The rotational states and their energies for a model of a ringlike molecule are studied. It is found that the discrete cylindrical symmetry of the molecule gives rise to a new quantum number in addition to that for the usual quantized angular momentum m. This new quantum number is formally analogous to but differs physically from the Bloch wave number for a one-dimensional crystal. The rotational states and energies of this model are discussed.
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03.65.-w Quantum mechanics
30.00.00 ATOMIC AND MOLECULAR PHYSICS

First-order partial differential equations in classical dynamics

B. R. Smith, Jr.

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1147 | Cited 2 times

Online Publication Date: Nov 2009

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Carathèodory’s classic work on the calculus of variations explores in depth the connection between ordinary differential equations and first-order partial differential equations. The n second-order ordinary differential equations of a classical dynamical system reduce to a single first-order differential equation in 2n independent variables. The general solution of first-order partial differential equations touches on many concepts central to graduate-level courses in analytical dynamics including the Hamiltonian, Lagrange and Poisson brackets, and the Hamilton–Jacobi equation. For all but the simplest dynamical systems the solution requires one or more of these techniques. Three elementary dynamical problems (uniform acceleration, harmonic motion, and cyclotron motion) can be solved directly from the appropriate first-order partial differential equation without the use of advanced methods. The process offers an unusual perspective on classical dynamics, which is readily accessible to intermediate students who are not yet fully conversant with advanced approaches.
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47.00.00 Fluid dynamics

Time series analysis with the Hilbert–Huang transform

Denis Donnelly and Edwin Rogers

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1154

Online Publication Date: Nov 2009

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Time series data can be transformed to the frequency domain via the Hilbert–Huang transform. This transform has two major stages. The data are first deconstructed into a set of monocomponent intrinsic mode functions that are the basis states for the transform. A Hilbert spectral analysis is then performed on each of these basis states, yielding time dependent amplitude and frequency information. The process of extracting the intrinsic mode functions and performing Hilbert spectral analysis is described and applied to a set of examples that show the advantages and shortcomings of this transform.
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02.00.00 Mathematical methods in physics
07.05.Kf Data analysis: algorithms and implementation; data management

Those wonderful elastic waves

Vladimir K. Ignatovich and Loan T. N. Phan

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1162 | Cited 2 times

Online Publication Date: Nov 2009

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We consider elastic waves in isotropic and anisotropic media and discuss their polarization, speeds, reflection from interfaces with mode conversion, and surface waves. The waves are represented by a wave function. For isotropic media this representation greatly simplifies the theory. The reflection of quasitransverse waves in anisotropic media from a free surface is shown to be characterized by three critical angles.
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46.00.00 Continuum mechanics of solids

Equilibrium charge density on a thin curved wire

M. Hossein Partovi and David J. Griffiths

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1173

Online Publication Date: Nov 2009

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We address the electrostatic problem of a thin, curved, and cylindrical conductor (a conducting filament) and show that the corresponding linear charge density slowly tends to uniformity as the inverse of the logarithm of a characteristic parameter, which is the ratio of the diameter to the smaller of the length and minimum radius of curvature of the filament. An alternative derivation of this result based on energy minimization is given. These results follow from a general asymptotic analysis of the electric field components and potential near a charged filament in the limit of vanishing diameter. It is found that the divergent parts of the radial and azimuthal electric field components are determined by the local charge density, while the axial component is determined by the local dipole density. For a straight filament our results reduce to those known for conducting needles. For curved filaments, the configuration of charges and fields is no longer azimuthally symmetric, and there is an additional length scale arising from the finite radius of curvature of the filament. The basic uniformity result survives the added complications, which include an azimuthal variation in the surface charge density of the filament. As with the variations in linear charge density along the filament, the azimuthal variations vanish with the characteristic parameter, only more rapidly. These findings allow us to derive an asymptotic formula for the capacitance of a curved filament that generalizes a result first obtained by Maxwell. The examples of a straight filament with uniform and linearly varying charge densities and a circular filament with a uniform charge distribution are treated analytically and found to agree with the general analysis. Numerical calculations illustrating the slow convergence of linear charge distribution to uniformity for an elliptical filament are presented. An interactive computer program implementing and animating the numerical calculations is available.
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41.00.00 Electromagnetism; electron and ion optics

Simple mechanical analogs of rapid adiabatic passage in atomic physics

B. W. Shore, M. V. Gromovyy, L. P. Yatsenko, and V. I. Romanenko

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1183 | Cited 4 times

Online Publication Date: Nov 2009

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We discuss two mechanical systems in which the approximate equations of motion are the same as the rapid adiabatic passage of a two-state quantum-mechanical system, such as that which occurs with quasistatic interactions and from the quasiperiodic action of a chirped-frequency laser pulse. We discuss a pair of masses on springs, weakly coupled by another spring, one of whose spring constants varies slowly, and a pair of coupled pendula, where the length of one pendulum slowly changes. In each example an approximation analogous to the rotating-wave approximation used in the corresponding quantum system brings the second-order macroscopic equations of motion into first-order form, and a slow variation in a system parameter characteristic leads to adiabatic change and rapid adiabatic passage.
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01.50.My Demonstration experiments and apparatus
03.65.-w Quantum mechanics
30.00.00 ATOMIC AND MOLECULAR PHYSICS
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The magnetic field produced at a focus of a current-carrying conductor in the shape of a conic section

C. Christodoulides

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1195

Online Publication Date: Nov 2009

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We determine the magnetic field at the focus of a conic section due to a current along the conic section. For a given current I, it is shown that this magnetic field is the same and equal to μ0I/2p for all conics with the same semilatus rectum p.
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41.00.00 Electromagnetism; electron and ion optics
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Handbook of Acoustics

Thomas D. Rossing, Editor and Leo L. Beranek, Reviewer, Reviewer

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1197

Online Publication Date: Nov 2009

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Abstract Unavailable
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01.30.Vv Book reviews
43.00.00 Acoustics

BOOKS RECEIVED

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. 1197

Online Publication Date: Nov 2009

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Volume 77 Index

American Journal of Physics -- December 2009 -- Volume 77, Issue 12, pp. I1

Online Publication Date: Nov 2009

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