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One step beyond the electric dipole approximation: An experiment to observe the 5p???6p forbidden transition in atomic rubidium
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| Pengarang | : | F. Ponciano-Ojeda; S. Hernández-Gómez; C. Mojica-Casique; E. Ruiz-Martínez; O. López-Hernández; R. Colín-Rodríguez; F. Ramírez-Martínez; J. Flores-Mijangos; D. Sahagún; R. Jáuregui; J. Jiménez-Mier |
| Nama Majalah/Jurnal | : | American Journal of Physics |
| Volume / Edisi | : | 86 (No. 1) |
| Halaman | : | 7-13 |
| Abstrak | : | An advanced undergraduate experiment to study the 5?3/2→6?3/2 electric quadrupole transition in rubidium atoms is presented. The experiment uses two external cavity diode lasers, one operating at the D2 rubidium resonance line and the other built with commercial parts to emit at 911 nm. The lasers produce the 5?→5?→6? excitation sequence in which the second step is the forbidden transition. Production of atoms in the 6?3/2 state is observed by detection of the 420 nm fluorescence that results from electric dipole decay into the ground state. Lines whose widths are significantly narrower than the Doppler width are used to study the hyperfine structure of the 6?3/2 state in rubidium. The spectra illustrate characteristics unique to electric dipole forbidden transitions, like the electric quadrupole selection rules; they are also used to show general aspects of two-color laser spectroscopy such as velocity selection and hyperfine pumping. |
Determination of the Coefficient of Thermal Expansion by Measuring Frequency of a Heated Music Wire
| Pengarang | : | Sambada, FA.Rusdi |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 62 (No. 2) |
| Halaman | : | 142-144 |
| Abstrak | : | Engaging with physical and material properties through empirical observation is a fundamental part of undergraduate physics and engineering education. Several works have proposed experiments to determine thermal physical constants of materials, such as finding the coefficient of linear expansion.1–4 As Dajbych5 and Polak et al.6 have shown, physical constants can be verified by measuring the frequency of a plucked high-carbon steel wire on a guitar. Building on our previous work,6,7 we have extended our method to verify the coefficient of linear thermal expansion, αT, through an accessible procedure directed at introductory physics education. To do this, we heated a guitar wire by running a current through it, causing the string to expand and resulting in a measurable decrease in frequency. Using only a DC power source, an acoustic guitar, two digital multimeters, and a cell phone, students can calculate the coefficient of thermal expansion... |
Switch Mechanism When Spinning the Magnetic Gyro Wheel
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 62 (No. 2) |
| Halaman | : | 139-141 |
| Abstrak | : | The magnetic gyro wheel is a toy where you can accelerate a spinning wheel to quite fast rotations. In the design discussed here, the wheel is spinning on two circular metallic frames and held to these by magnets (see Fig. 1). Because the spindles on the wheel are small compared with the circular frames, the wheel will perform many revolutions within one rotation on the frame. When the wheel spins fast enough, a switch mechanism will turn on an LED light to make it even more spectacular. |
Enhanced Rolling Moment of Inertia Demonstration
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 62 (No. 2) |
| Halaman | : | 135-138 |
| Abstrak | : | Moment of inertia is often illustrated using the classic demonstration of a solid cylinder and a hollow cylinder with identical mass and radius rolling down an incline, in which the solid cylinder has a linear acceleration 4/3 times that of the hollow cylinder. This article describes an extreme version of this apparatus with a rolling object that has an acceleration more than 25 times that of an object of identical mass and rolling radius. This apparatus would be suitable as a lecture demonstration or as an intermediate-level laboratory project. |
Rolling with Slipping and Transition to Pure Rolling on an Inclined Plane
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 62 (No. 2) |
| Halaman | : | 132-134 |
| Abstrak | : | To illustrate the problem studied in this paper, we will use a scenario in which five rigid disks move in a race on an inclined plane. First, they slip and, after a particular time, they only roll. The friction forces between each disk and the plane are distinct, and their values increase from disk 1 to disk 5. In this situation, how long does a disk take to enter a pure rolling motion? What are the requirements for this motion transition to occur? Which disk will have more energy when reaching the finishing line if they all arrive without slipping (i.e., pure rolling)? Most undergraduates, even some physics teachers, would indicate disk 1. However, the result may surprise them. |
Using the Pickering Polarimeter Today
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 62 (No. 2) |
| Halaman | : | 130-131 |
| Abstrak | : | The polarimeter is a device for viewing optically active material that is held between two crossed polarizing filters. For many years, I made my own version of this to allow my entire class to see the effects. A sheet of Polaroid was laid on the top surface of an overhead projector. A second sheet was held a short distance above the first one, and the object to be studied was placed between the two sheets.1 The original polarimeter was described in 1873 by William C. Pickering of the Massachusetts Institute of Technology.2 Later on in this note, I will discuss his design, and also Pickering’s widely used book on experimental techniques for undergraduate physics instruction. |
The Different Colors Displayed by a Circular Polarizing Filter
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 62 (No. 2) |
| Halaman | : | 127-129 |
| Abstrak | : | Polarization is an important concept in physics, and physics teachers have developed many experiments using the principle of polarization.1–4 We discovered an interesting phenomenon (Fig. 1) in the use of a circular polarizing filter (CPL), which is a photographic accessory installed in front of the camera lens to eliminate polarized light in the environment. When a CPL is placed on a steel breadboard, it looks blue, and when placed on a piece of paper, it appears dark gray. The principles of polarization can be used to explain the interesting phenomenon. |
Damped Oscillations—A Smartphone Approach
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 62 (No. 2) |
| Halaman | : | 123-126 |
| Abstrak | : | We report the study of an oscillating pendulum under various damping conditions. A smartphone was used as a pendulum and, at the same time, as a data recorder. Results show that the smartphone is an effective and reliable tool for performing educational activities, providing students with a variety of ways to learn new content and physical concepts. It offers the opportunity to carry out experiments in the classroom, laboratory, or at home. In the experiments performed, increasing the cross-sectional area of the pendulum increases the damping coefficient slightly, and rapidly decreases the oscillation amplitude as time passes. Results suggest that the time necessary to decrease the amplitude by half is inversely proportional to the cross-sectional area of the pendulum. As expected, there was no significant variation in the period nor the angular frequency as the amplitude changed due to the air–pendulum drag properties and the slow pendulum speed. |
Learning about Climate Change and Decline of Biodiversity by Constructing a Qualitative Representation
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 62 (No. 2) |
| Halaman | : | 119-122 |
| Abstrak | : | We have developed a lesson in which learners interactively construct a qualitative representation about climate change and the decline of biodiversity by using the online software DynaLearn.1 They are supported by a built-in support function to notice mistakes, and they can run simulations to explore system behavior. Throughout the lesson, learners are guided by a workbook providing necessary information step by step. Climate change is a complex problem. There are several studies that describe common misconceptions of learners about the greenhouse effect and related processes.2–4 An example of this is that many learners do not perceive Earth as a radiating entity. Instead, they believe that the atmosphere is acting as a shield, trapping heat as “solar radiation.” Furthermore, learners frequently lack an understanding of the distinction between the natural and enhanced greenhouse effect. |
COVID-19 Questions for Physics Exams
| Pengarang | : | - |
| Nama Majalah/Jurnal | : | The Physics Teacher |
| Volume / Edisi | : | 62 (No. 2) |
| Halaman | : | 116-118 |
| Abstrak | : | Physics instructors are always looking for questions and activities that both are tractable to students and illuminate real-life applications of physics. This is especially true in Introductory Physics for the Life Sciences (IPLS), where many students enter with the belief that physics is merely a “weed-out” course that has little to do with their majors and career goals.1 Authentic applications of physics to the life sciences help dispel this myth. The COVID-19 pandemic provides numerous examples of the relevance of physics to current events and the life sciences. Physics principles are used both to model the spread of the disease and to develop technologies that curb its transmission. Given the disruption COVID-19 has wrought on almost every aspect of life, physics content related to the pandemic inevitably captures students’ attention. Few topics are more relevant to their lives, at the time of writing, than COVID-19. |