November 2022 Issue,
Volume 90, No. 11
We present a set of experiments and computations suitable for introducing upper-level undergraduate physics and engineering students to the interdisciplinary field of nanoplasmonics for periods ranging from a week-long advanced laboratory session to a summer research project. The end product is a tunable optofluidic device capable of detecting changes in a fluid medium as low as 0.002 refractive index units. The sensing element—a thin gold film on a glass prism coupled to a microfluidic cell—owes its sensitivity to the bound nature of the surface plasmon–polariton waves that are resonantly excited by evanescently coupled light at the gold–fluid interface. Pedagogically, surface plasmon resonance (SPR) sensing immerses students in the rich physics of nanoscale optics and evanescent waves in constructing and operating a precision apparatus and in developing theoretical, analytical, and numerical models to aid both in the physical understanding and engineering optimization of the SPR sensor.
In this issue: November 2022 by John Essick, Claire A. Marrache-Kikuchi, Beth Parks, B. Cameron Reed, Donald Salisbury and Todd Springer. DOI: 10.1119/5.0126945
LETTERS TO THE EDITOR
A vectorial analysis of the “Golfer's Nemesis” by Kirk T. McDonald. DOI: 10.1119/5.0124266
Reply to Kirk McDonald by Olivier Pujol. DOI: 10.1119/5.0124948
Motion of a charged particle in the electric field of a uniformly charged finite wire by Kirk T. McDonald. DOI: 10.1119/5.0124271
Falling toast by Rod Cross. DOI: 10.1119/5.0127740
Causality, determinism, and physics by Julio Gea-Banacloche. DOI: 10.1119/5.0087017
The language of cause and effect is deeply important to classroom physics instruction, and curious students seek to understand the meaning and implications of these terms. This essay offers historical insights, an overview of the current debate, and an extensive bibliography that can enrich classroom discussion on this topic.
Using Hexbugs™ to model gas pressure and electrical conduction: A pandemic-inspired distance lab by Genevieve DiBari, Liliana Valle, Refilwe Tanah Bua, Lucas Cunningham, Eleanor Hort, Taylor Venenciano and Janice Hudgings. DOI: 10.1119/5.0087142
Hexbugs are toy automatons that move in straight lines until they reach an obstacle, after which they are randomly scattered and continue their journey. As such, they can be used to model randomly moving physical objects: gas particles or electrons for instance. This paper proposes to revisit some thermodynamics and statistical mechanics concepts in the laboratory using these toys. The authors describe an undergraduate modern physics distance lab course, implemented during the COVID-19 pandemic, where students grasp a better understanding of the ideal gas law and of the Drude model by simulating microscopic behaviors with macroscopic objects. This work is also an invitation to rethink our lab teaching practice and focus on developing students’ experimental research skills by letting them investigate a topic of their choosing.
Turbulent dispersion of breath by the wind by Florian Poydenot, Ismael Abdourahamane, Elsa Caplain, Samuel Der, Antoine Jallon, Inés Khoutami, Amir Loucif, Emil Marinov and Bruno Andreotti. DOI: 10.1119/5.0064826
The dispersal of aerosols is a century-old problem that was brought to the forefront of our attention by the COVID-19 pandemic. The combination of turbulence with the bulk motion of air that was found to exist in many large indoor spaces yields unexpected results that are characterized in this paper. This work introduces non-experts to concepts in fluid mechanics and could easily lead to a variety of future student projects. A video abstract accompanies the online version of this paper.
Free fall of a quantum many-body system by A. Colcelli, G. Mussardo, G. Sierra and A. Trombettoni. DOI: 10.1119/10.0013427
The motion of freely falling object is one of the first systems students encounter in classical mechanics. The analogous quantum problem is often omitted in introductory quantum physics courses as the energy eigenfunctions involve unfamiliar special functions. This paper builds on previous studies employing operator methods to gain physical insight into this quantum mechanical problem in a much more accessible way, requiring no arcane functions. Some important generalizations are made, including the application to freely falling systems of more than one quantum particle. The paper contains material of interest to a wide range of readers: from undergraduates first learning about operators to experts in quantum many-body theory.
Submarine paradox softened by Hrvoje Nikolić. DOI: American Journal of Physics 90, 841 (2022); https://doi.org/10.1119/5.0084185
A drop of ink is immersed in a completely still lake. Suppose the density of the ink is such that it neither sinks nor floats when it is at rest. Now, what happens if the ink moves relativistically with respect to the water: Does it sink or float? Explorations of the subtleties of relativistic buoyancy have been published over the years; the original “submarine paradox” of this type was posed in this journal over 30 years ago. This article brings a new dimension to such questions as it employs general relativistic fluid dynamics to develop the answer. A student who has taken a course on general relativity will find they possess the mathematical skill needed to understand the details of the paper, and all readers will certainly enjoy wrestling with such conceptual puzzles.
Long-term changes in the Earth's climate: Milankovitch cycles as an exercise in classical mechanics by R. C. T. Rainey. DOI: 10.1119/10.0013563
The Milankovitch cycles are periodic changes in the earth’s orbit that are believed to be responsible for the ice age cycles over the last million years. The cycle with the strongest effect on climate modulates the tilt of the earth’s spin axis with respect to its orbital plane. This paper shows how the periods of these cycles can be calculated through a fairly simple method, suitable for an advanced undergraduate mechanics course.
NOTES AND DISCUSSIONS
Simple precession calculation for Mercury: A linearization approach by Michael J. W. Hall. DOI: 10.1119/5.0098846
The explanation of the anomalous perihelion precession of Mercury is one of the crown jewels of general relativity. Unfortunately, analyses of this effect require advanced mathematics, with essential steps often having to be supplied to students. This paper develops an approximate treatment of the precession effect by linearizing the relativistic orbital equation, which puts it in a form very similar to that for a Kepler orbit. The precession effect can then be extracted in a straightforward manner without having to invoke perturbation analyses or complicated integrals. Appropriate for introductory classes in general relativity.
Comment on projectile motion with quadratic drag using an inverse velocity expansion by Antonio Corvo. DOI: 10.1119/5.0097411
This paper shows how an unconventional Taylor series expansion can be used to obtain trajectories for projectile motion in the presence of quadratic drag. This method provides students with practice in expansion methods and allows insight into the factors that are important to modeling trajectories measured in classroom demonstrations or the teaching laboratory.
INSTRUCTIONAL LABORATORIES AND DEMONSTRATIONS
Surface plasmon resonance sensing in the advanced physics laboratory by Alaa Adel Abdelhamid, David Kerrigan, William Koopman, Andrew Werner, Zachary Givens and Eugenii U. Donev. DOI: 10.1119/5.0070022
A set of nanoplasmonics-based experiments for detecting minuscule changes in the refractive index of a fluid is presented. The experimental setup implements the Kretschmann-Raether configuration using a commercially available surface plasmon resonance substrate (glass prism with a titanium/gold film coating) and microfluidic cell (for flow of solutions along the substrate's metal film surface), thus significantly lowering the sample fabrication barrier to implementation. The paper provides instructions for performing the experiments as well as a detailed theoretical and computational background. The work described here offers an accessible project–the surface plasmon resonance phenomenon–for the undergraduate instructional laboratory.