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Resource Letter: Synthesis of the elements in stars
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| Pengarang | : | Artemis Spyrou |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 92 (No. 10) |
| Halaman | : | 731-736 |
| Abstrak | : | This Resource Letter provides a guide to the literature on the field of nuclear astrophysics, and particularly the origin of the elements. Nuclear astrophysics is a multidisciplinary field that aims at understanding where everything we see around us comes from and how it came to be. Astronomical observations, astrophysics modeling, and nuclear physics experiment and theory come together to answer important questions like: Where and how are the elements created? How do stars evolve? What drives the different types of stellar explosions? What is left behind after the cataclysmic death of a star? This Resource Letter presents our current understanding of the origin of the various chemical elements, together with modern research and new developments in the field, with a particular focus on the measurement of nuclear properties for astrophysical applications. |
Bringing graphene into the undergraduate classroom
| Pengarang | : | Andrew Seredinski; Tedi Qafko; Nathanael Hillyer; Alexander Norman |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 92 (No. 9) |
| Halaman | : | 703-710 |
| Abstrak | : | We present an undergraduate instructional laboratory experiment that introduces students to the most well-known van der Waals material, graphene. Like all van der Waals materials, graphene is a crystal that can be peeled into layers, in some cases, down to atomic thicknesses. In this experiment, students first fabricate a sample consisting of few-layer graphene flakes atop of a silicon wafer substrate using the mechanical exfoliation method. The students then use a microscope setup to acquire images of the sample under white-light and LED illumination. These images are analyzed to produce optical contrast values (a measure of the reflectance of the graphene flakes) as a function of illumination wavelength. A theoretical model for optical contrast is developed based on thin-film interference and the resulting theory and experiment are compared, yielding a value for the graphene flake's thickness. This experiment is designed for advanced instructional laboratory and upper level optics courses. It may also be simplified into a qualitative introductory physics laboratory, demonstration, or outreach workshop activity. |
Probing coherent phonons in the advanced undergraduate laboratory
| Pengarang | : | Nicholas J. Brennan; Joseph Peidle; Anna Wang-Holtzen; Jieping Fang; Kathryn Ledbetter; Matteo Mitrano |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 92 (No. 9) |
| Halaman | : | 693-702 |
| Abstrak | : | Ultrafast optical spectroscopy is an effective experimental technique for accessing electronic and atomic motions in materials at their fundamental timescales and studying their responses to external perturbations. Despite the important insights that ultrafast techniques can provide on the microscopic physics of solids, undergraduate students' exposure to this area of research is still limited. In this article, we describe an ultrafast optical pump-probe spectroscopy experiment for the advanced undergraduate instructional laboratory, in which students can measure coherently excited vibrations of the crystal lattice and connect their observations to the microscopic properties of the investigated materials. We designed a simple table-top apparatus based on a commercial Er-fiber oscillator emitting 50-fs pulses at 1560 nm and at 100 MHz repetition rate. We split the output into two beams, using one of them as an intense “pump” to coherently excite phonons in selected crystals, and the other as a weaker, delayed “probe” to measure the transient reflectivity changes induced by the pump. We characterize the ultrafast laser pulses via intensity autocorrelation measurements and detect coherent phonon oscillations in the reflectivity of Bi, Sb, and 1T-TaS2. We then discuss the oscillation amplitude, frequency, and damping in terms of microscopic properties of these systems. |
Understanding exotic black hole orbits using effective potentials
| Pengarang | : | Steven Pakiela; Brett Bolen; Benjamin P. Holder; Monica Rizzo; Shane L. Larson |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 92 (No. 9) |
| Halaman | : | 686-692 |
| Abstrak | : | Strongly gravitating systems can undergo unusual orbital trajectories. For example, “extreme mass ratio inspirals” (observable in the megahertz band by space-based gravitational wave detectors) can exhibit “zoom-whirl” orbits, which make complicated waveforms that are useful for mapping out the system's gravitational structure. Zoom-whirl behavior can be intuitively understood in the context of effective potentials, which should be familiar to students from classical orbital theory in mechanics. Here, we explore zoom-whirl orbits using effective potential theory around Schwarzschild black holes and present an interactive tool that can be used in pedagogical settings. |
Remarks on the yield of fission bombs
| Pengarang | : | J. M. Pearson; B. Cameron Reed |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 92 (No. 9) |
| Halaman | : | 680-685 |
| Abstrak | : | We discuss the apparent paradox that the energy released in a fission bomb explosion is independent of the energy ? liberated by each fissioning nucleus. The paradox is resolved by noting that a larger value of ? results in a shorter “burn time”; this stops the chain reaction sooner and results in fewer nuclei being fissioned. |
Photon under repeated transverse Lorentz boosts: An apparent paradox
| Pengarang | : | Tugdual LeBohec |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 92 (No. 9) |
| Halaman | : | 674-679 |
| Abstrak | : | We investigate the effects of the repeated application of Lorentz boosts to the four momentums of a photon in the transverse direction and observe that this can take us to a reference frame in which the direction of the photon's momentum is apparently reversed. This raises an apparent paradox: how could two observers see the same photon traveling in opposite directions? We further extend this process to an infinite succession of infinitesimal transverse Lorentz boosts and show it amounts to a rotation of the photon's momentum, but as part of a Lorentz transformation and not as a simple rotation. These possibly surprising results can be understood in light of the Wigner rotation: the combination of Lorentz boosts along different directions amounts to a Lorentz boost combined with a rotation. The presented exercises offer illustrations of the counterintuitive behavior of Lorentz boost combinations. |
A linear-algebraic derivation of the Lorentz transformation
| Pengarang | : | Phil Schwartau |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 92 (No. 9) |
| Halaman | : | 670-673 |
| Abstrak | : | In order to explain the Lorentz transformation, it is advantageous to use its eigencoordinates rather than Cartesian coordinates. In this manner, the matrix can be diagonalized. Moreover, the diagonal entries have a direct physical meaning—permitting their determination without the need of algebraic equations. This yields a proof that is easier to remember and reproduce. |
Application of the heat equation to the study of underground temperature
| Pengarang | : | Mathis Caprais; Oriane Shviro; Ugo Pensec; Hermann Zeyen |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 92 (No. 9) |
| Halaman | : | 663-669 |
| Abstrak | : | Modeling underground temperatures provides a practical application of the one-dimensional heat equation. In this work, the one-dimensional heat equation in surface soil is extended to include heat carried by the vertical flow of rainwater through the soil. Analytical solutions, with and without water flow, illustrate the influence of rainwater circulation on the sub-surface propagation of seasonal temperature variations, an important effect that is generally neglected in textbooks. The surface temperature variations are damped by the soil, and this effect was used by the Troglodytae in Egypt or the Petra in South Jordan to insulate against extreme temperatures. For a realistic case of horizontally layered geology, a finite volume Python code was developed for the same purpose. Subsurface temperatures were also measured over a full year at depths up to 1.8 m and used to estimate the thermal skin depth and thermal wavelength. This study provides students with a practical example of how a textbook physics problem can be modified to extract information of contemporary importance in geophysics and global warming. |
Data science education in undergraduate physics: Lessons learned from a community of practice
| Pengarang | : | Karan Shah; Julie Butler; Alexis V. Knaub; An?l Zengino?lu; William Ratcliff; Mohammad Soltanieh-ha |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 92 (No. 9) |
| Halaman | : | 655-662 |
| Abstrak | : | It is becoming increasingly important that physics educators equip their students with the skills to work with data effectively. However, many educators may lack the necessary training and expertise in data science to teach these skills. To address this gap, we created the Data Science Education Community of Practice (DSECOP), bringing together graduate students and physics educators from different institutions and backgrounds to share best practices and lessons learned from integrating data science into undergraduate physics education. In this article, we present insight and experiences from this community of practice, highlighting key strategies and challenges in incorporating data science into the introductory physics curriculum. Our goal is to provide guidance and inspiration to educators who seek to integrate data science into their teaching, helping to prepare the next generation of physicists for a data-driven world. |
Resource Letter ALC-1: Advanced Laboratory Courses
| Pengarang | : | Walter F. Smith |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 92 (No. 9) |
| Halaman | : | 648-654 |
| Abstrak | : | Advanced laboratory courses play several essential roles in the undergraduate curriculum, including the development of students into independent experimentalists. This Resource Letter provides an overview of the typical structure and learning goals of advanced laboratory courses. It then details the books, organizations, online resources, equipment vendors, and assessment tools that are available to support such courses. There are so many journal articles on this topic that it is impractical to summarize them in this article, although several of the most central ones are highlighted. Instead, a categorized database of these articles has been created and will be kept updated. |