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This article illustrates a learning sequence from the Interdisciplinary Mathematics and Science (IMS) Learning project, connecting science and mathematics learning in the primary school. Exploring light and its properties involved a series of investigations conducted in Grades 4 and 5 across three classes in two schools in regional Victoria. The teachers implemented an inquiry-based pedagogical model to guide students' spatial reasoning by exploring angle, symmetry, rotation, 2D diagrams and 3D models in an investigation of light reflection, using multiple representations. Students developed ideas from a "maze challenge" used in their design of a periscope.

In this paper, a simple method is described for visually demonstrating that the wavelength of light reduces when entering a medium of higher refractive index. When a violet laser (405 nm) is reflected off the surface of a Blu-ray disc (track spacing 320 nm) diffraction cannot occur since the wavelength is greater than the track spacing. However, in water (refractive index 1.33) the wavelength of violet light reduces to 304.5 nm and therefore first-order diffraction can occur when a violet laser is reflected off a Blu-ray disc submerged in water. A violet laser was reflected off a DVD in air, and one diffraction order was seen, but two orders were observed when the disc was immersed in water. Red, green, and violet lasers were reflected off CD, DVD and Blu-ray discs and the number of observed diffraction orders compared with theory. When a violet laser was reflected off a CD in air, three diffraction orders were seen, however five orders were observed in water. The use of tonic water in the experiments enabled the diffraction orders to be seen more easily because violet light causes the quinine in tonic water to fluoresce.

The Arduino board and its communication with several sensors are becoming more and more popular in the physical science community. They offer inspiring possibilities for learning different physical concepts. In this article, we focused on creating a very practical educational system for experimenting with diffraction of laser light and graphically visualizing the distribution of light intensity in space, which is impossible to perform it with the devices available in the educational laboratories of physics. The main elements of this configuration are the Arduino UNO microcontroller board, the BH1750 sensor and the NEMA17 motor and its A4990 driver. The results' graph is displayed in real time on the computer using the Data Streamer add-in. We see that the abbreviated curve corresponds well to the theory. In addition, feedback from the participants in the test activity of the device showed that they were satisfied with its operation and its contribution to the understanding of diffraction. Therefore, we believe that the device presented can play a very important role in the diffraction phenomenon learning because of its high precision and reliability in the measurements.

In Japan, research activities by junior and senior high school students show an upward trend. However, there are limited examples of research activities in the field of elementary particles and atoms. This is due to the difficulty associated with procuring research tools such as accelerators or particle detectors. Therefore, we hosted the 'Accel Kitchen' in 2018 and 2019 at the Cyclotron and Radioisotope Center (CYRIC) in Tohoku University where junior and senior high school students could participate in ongoing research of particle and atomic physics. At each workshop, 12 junior and senior high school students participated in the beam experiment, including the production of francium atoms (Fr) by the fusion reaction of oxygen and gold, optimizing the transport of the ion beam and identifying the alpha decay nuclei, and laser trapping of Fr for two days. Each group that was involved in the experiment was supported by researchers and university students who acted as mentors. This was the first opportunity for junior and senior high school students to know about the particle beam experiment in Japan.

In this paper, we propose a simple yet generic and versatile method to measure the position of a moving body as a function of time. Apart from very basic equipment such as carts and wheels, only a laser pointer or a similar device and a smartphone are necessary. By attaching a source of light to a cart and video filming its movement on a horizontal plane under the gravitational force, the position of the cart as a function of time can be recorded without any calibration and using one of the many free apps. The obtained results for the cart acceleration under a constant force were in very good agreement with Newton's second law. The inexpensive equipment and the possibility of taking data at very short intervals allow different experiments in mechanics to be performed, for example to demonstrate the conservation of energy and momentum in mechanics or to investigate complex movements.

In this article, the author presents a Desmos activity where students adjust the measures of angles in radians to reposition a laser and a mirror so the beam passes through three stationary targets. This Radian Lasers activity can be extended to simulate project-based learning (PBL), a pedagogical approach for applying concepts and skills from various disciplines to a specified project. Students apply what they learn about angle measure and light reflection by designing a periscope.

A single-slit diffraction experiment in an introductory physics laboratory is generally comprised of a rectangular slit and a laser source. The laser beam is sent to the slit producing the well-known diffraction pattern on the screen. This paper proposes a simple modification of the single-slit diffraction experiment to increase student attention about the laser beam and its diffraction. A single slit can be used to measure laser beam width. The beam width measurement is demonstrated by using a 632.8 nm Helium Neon (HeNe) laser. In this experiment, the laser beam is assumed as a Gaussian beam. The beam width is determined by scanning in one direction across the laser beam. The measurement results are shown to achieve satisfactory results when compared with a commercial laser beam profiler. By measuring the laser beam widths, students will qualitatively observe that the laser beam width increases along propagation distance. This experiment can be an additional exercise in a single-slit diffraction experiment.

The laser pointer has been widely used to demonstrate some simple optics phenomena, like reflection, refraction, total reflection, and diffraction. However, the rays of laser light cannot be seen in the air because the scattered light is too weak. Many physics teachers use milk or smoke to visualize rays of laser light in physics labs, but it is hard to demonstrate some experiments, such as diffraction. Recently, Velasco and del Mazo demonstrated an interesting experiment in which four optical phenomena could be visualized by using a rhodamine B solution. However, the color change of the laser beam (532 nm) is not easy to explain for students who have just learned optics. In this study, we developed a simple way of visualizing geometric optical experiments in water mixed with highlighter ink to eliminate the influence of color change. Our material list includes a green highlighter, a large transparent rectangular tank filled with water, a smaller transparent square container, a round acrylic plate, a prism, a concave acrylic plate, a beaker, and a CD grating.

The typical sound of George Lucas' laser blaster in the "Star Wars" series is well known. What does a laser blaster in "Star Wars" sound like, and why? Here we show a simple way to produce this sound by using low-cost lab material, like a spring or a Slinky. Building on the work of Crawford, who analyzed the sound of a Slinky using oscilloscopes, we present a technique for analyzing the sound using mobile devices. For a deeper quantitative analysis, a PC with open-source software is used.

The refractive index is a number that governs how light changes its direction of propagation as it enters one material medium from another. This phenomenon is known as refraction and the angles of incidence and refraction of light, referred to the normal to the interface of the two media at the point of incidence, are related by Snell's law. The refractive index (RI) depends on the color (or wavelength [lambda]) of light. Tables of values of refractive indices for various media and wavelengths of light, with respect to vacuum, are readily available. The refractive index of a material can be measured by many methods, for example, by using a spectrometer in conjunction with a prism made of the experimental substance. An important class of methods of measuring RI involves the formation of interference patterns. Interferometric measurements are concerned with the study of separation between bright fringes (or dark fringes) resulting from the superposition of light waves, originating from a single source and propagating along paths of different optical lengths (refractive index multiplied by geometric path length). Researchers have exploited (nearly) monochromatic light from laser sources to enhance precision in measuring refractive index by applying interferometric techniques.

This article describes a simple way to introduce nanomaterials using the presence of carbon nanodots (CNDs) in widely available food. Budweiser® beer and Coca-Cola®, commercial foods that are commonly accessible, were utilized to demonstrate the optical property of nanoparticles. Specifically, green and violet laser pointers were employed for the observation of excitation-dependent photoluminescence of CNDs. To represent the application of CNDs, we obtained multiple-color emissions in onion cells that were imaged by using Budweiser beer and Coca-Cola as a dye. The demonstration could offer a perspective on the use of food in teaching nanomaterials at the high school and undergraduate levels.

Laser-induced breakdown spectroscopy (LIBS) and principal component analysis (PCA) are frequently used for analytical purposes in research and industry, but they seldom are part of the chemistry curriculum or laboratory exercises. This case study paper describes the combined application of LIBS and PCA during a research internship for an undergraduate student. The instructional method applied was based on a one-on-one mentorship, in which case the learner was engaged in a research work. The learning activities included theoretical introductions to the LIBS and PCA methods, numerical simulation, experiments, and data analysis. The study covered three main topics: analysis of LIBS spectra, application of PCA for clustering, and use of PCA for experimental design. The realization of the study was instructive for all parties involved: from the mentorship point of view, it is concluded that the topics can be covered during an internship or developed into a one semester long research-based module of a chemistry program or a final year project. The student, on the other hand, developed profound technical skills in performing experiments and using PCA software for data analysis.

Huygens' principle in which every point on a propagating wave acts like a point source of radiation is a foundation principle of physics. Normally, Huygens' principle is demonstrated by passing a wave, for example a water or light wave through an aperture comparable in size to the wavelength. In this paper, an experiment is described in which a 0.1 mm diameter copper wire is placed in front of a laser pointer to demonstrate Huygens' principle in empty space. The diffraction pattern was photographed using a phone camera, and the bandwidth measured using a free image analysis program, ImageJ. The diffraction diameter of the wire was 0.095 ± 0.005 mm. The experiment can easily be performed in a classroom.

In this paper, we present simple demonstrations aimed at explaining the fundamental principles of the photoacoustic effect. To display the audible phenomenon that occurs as laser radiation gets absorbed by ethene gas, an optical chopper was used to modulate the power of a continuous-wave laser whose beam was directed into a gas. The absorbed pulses of laser light resulted in time, harmonic, temperature, and pressure perturbations that excited the resonator, eliciting an acoustic response at its fundamental resonance frequency and harmonics. Multiple variables were changed to determine their effect on the photoacoustic signal and to replicate similar factors that influence the tones produced by musical instruments. Videos of the oscilloscope were recorded for various musical notes and then assembled into a combined demonstration video. This demonstration can be used to generate greater interest in the sciences as well as explain fundamental concepts that are at work in this experiment to students. The results of the student survey in General Chemistry 2 lectures show that the demonstration videos were useful resources.

Possibly the greatest irony of physics education is the difficulty of demonstrating optics in a visible way. The two most common solutions to this conundrum are to either use "all-inclusive" optical apparatuses, like a large-format camera, or to rely on classic ray-tracing diagrams. While the former looks elegant while demonstrating the inverted nature of its images at the front of a classroom, its inner workings and method of inverting remain mysterious. The mechanics of the latter are more evident but are limited to two dimensions and the willingness of students to accept the drawing as fact. More advanced solutions include computer modeling of 3D optics or benchtop ray-tracing demonstrations, but between these the demonstrator effectively trades a third dimension for verisimilitude. A more encompassing solution would be a means to trace rays in three dimensions through a variety of optical devices. Previously, the rub has been identifying a viable point source of rays for classroom demonstrations. In this paper, we present such a source and several sequences of demonstrations utilizing it. Traditionally, the standard method to produce a point source of rays is to mask a well-defined source, such as an FCR lamp. Masks can be as complicated as an opaque sphere with evenly spaced holes or as simple as the classic inverted colander. In all cases, these demonstrations are typically limited to only being used as rough examples of sources due to limitations in portability, homogeneity of rays, or simply total number of rays. Our recommended ray source provides hundreds of rays that are bright and uniformly distributed enough to perform geometric optics demonstrations, such as collimation, telescopes, and parabolic reflections.

Purpose: This systematic review aimed to analyze the effects of low-level laser therapy (LLLT) on the severity of tinnitus when compared to no therapy or other modalities of therapies. Method: A systematic review protocol was registered at the International Prospective Register of Systematic Reviews (PROSPERO) under the Registration Number CRD42019119376. A search was performed in each of the following databases: EMBASE, LILACS, PubMed, Science Direct, Scopus, Web of Science, Google Scholar, and ProQuest. The inclusion criteria consisted of studies in adults over 16 years of age, randomized clinical trials in which subjects presented chronic ([greater than or equal to] 6 months) and subjective tinnitus (unilateral or bilateral) as well as with or without bilateral sensorineural hearing loss, and studies that used only LLLT for treatment of tinnitus compared to no-therapy group or other modalities of therapy. No language or time restrictions were stipulated. The references were managed by Endnote Web and Rayyan QCRI. Results: After the screening process, seven studies remained that attained the eligibility criteria. Regarding the risk of bias, only one study was categorized as low risk of bias; the six remaining studies were classified as moderate risk of bias. The seven included studies mainly assessed the LLLT effects on tinnitus by Visual Analogue Scale, Tinnitus Handicap Inventory, pitch and loudness matching, minimum masking level, and pure-tone audiometry. All the seven selected studies found different degrees of significant results regarding tinnitus severity; however, there was no consensus among the results. Conclusion: Even though the LLLT showed positive effects in the tinnitus severity in some studies, it is not possible yet to make any recommendation over its uses for the treatment of tinnitus severity.

Contribution: A hybrid approach involving reduced lecture content with project-based learning (PBL) was introduced to a standalone course in optics at an engineering school not specialized in this area, with promising results. Background: At most schools, optics is an elective "niche" area involving a single senior course. This presents challenges, since the topic has breadth and depth, leaving little time for application projects. Yet, seniors want future applicability. After many years, the instructor questioned his "broad-brush" approach involving many topics with limited application, especially given the role of optics and photonics in technology leadership. A literature search uncovered recent use of project-based methods for optics in K-12 and community colleges but little use in U.S. universities, suggesting an opportunity. Intended Outcomes: The authors intended that achievement and valuation by students would be greater with authentic projects and less content. Application Design: Therefore, an approach that concentrated content and project work on light's dualistic nature in a mathematically rigorous manner was taken. With reduced content, class time was available for PBL, whereby the problem motivated the content. For light's wave nature, five lecture weeks were followed by a project simulating the propagation of light. For the particle nature, a circuit design project to implement analog electronic circuits during class occurred after five lecture weeks. Findings: Student interviews and instructor perspectives on impacts of learning, career preparation, graduate school interest, and in-class engagement uncovered encouraging results. A direct assessment showed significantly higher homework scores with the course changes.

The use of CO[subscript 2] laser cutters/engravers in technology and engineering education "allows even beginning students to produce professional parts in a very short time [and] empowers and motivates students, helping to bring out their creativity" (Flowers, 2000, p. 11). They are fast, accurate, fun to use, and they facilitate iterative design. Laser machining is essentially a two-dimensional (2D) process. The challenge described in this article was for students to create examples of different ways in which lasers can be used to fabricate products that have 3D geometry. This turned out to be a great vehicle for STEM integration and a tool for teaching process engineering. This article is a review of several ways laser cutters/engravers have been used in one technology and engineering program not just for 2D designs, but to design and prototype products that have three-dimensional (3D) geometry. This progression of ideas begins by addressing 2D geometry.

A popular physics legend holds that scissors can cut paper with a speed faster than light. Here this counter-intuitive myth is investigated theoretically using four simple examples of scissors. For simplicity, all cases will involve a static lower scissors blade that remains horizontal just under the paper. In the first case, the upper blade will be considered perfectly rigid as it rotates around and through the paper, while in the second case, a rigid upper blade will drop down to cut the paper like a guillotine. In the third case, the paper is cut with a laser rotating with a constant angular speed that is pointed initially perpendicular to the paper at the closest point, while in the fourth case, the uniformly rotating laser is pointed initially parallel to the paper. Although details can be surprising and occasionally complex, all cases allow sections of the paper to be cut faster than light without violating special relativity. Therefore, the popular legend is confirmed, in theory, to be true.

Although there are over 320,000 health and fitness apps available on major app stores, there is scant evidence that they actually promote a healthier lifestyle, assist users in exercising, or promote weight loss. This article presents a lesson plan using an Arduino for integrating computational thinking and game design with middle school students who may have little or limited prior experience with text based programming. Specifically, the authors believe that this lesson plan, which focuses on engaging students in both designing and playing an active laser-tag game (Figure 1, page 13), can help students learn basic programming principles, explore ideas related to circuits and sensors, develop teamwork and communication skills, participate in active physical play, and gain motivation in learning more programming in future game development and other applications.

This paper presents a new way to demonstrate the principle behind mirages in air in the lab. The setup is simple and includes a modified laser illuminator that allows direct comparison between the deflected light rays and their straight path.

This paper describes the use of a tabletop electron microscope in teaching college level physics. The workings and use of an electron microscope encompass many aspects of science, technology, engineering and mathematics (STEM). A sequence of activities was constructed to compliment the instructional material in the physics course of the University of Queensland Foundation Year. A Hitachi TM4000 scanning electron microscope was used to obtain images to measure the track spacing of CD, DVD and Blu-ray discs. The nominal track spacings are 1.6 µm, 740nm and 320nm for CD, DVD and Blu-ray discs, respectively, comparable to the wavelength of visible light and therefore give rise to visible diffraction effects. The track spacing for a CD and DVD was measured using red, green and blue laser pointers with an accuracy well under 10%. The experiments described in this paper demonstrate how a scientific instrument such as a scanning electron microscope can be used to integrate the teaching of different STEM areas.

This paper presents an argumentation-based demonstration experiment to teach the light-matter interaction using an observable laser beam and vacuum pump. In the experiment, the concept of darkness was addressed using a virtual space environment created by gradually decreasing the pressure inside a quartz glass bell jar with a vacuum pump. This experimental activity, offering an evidence-based inquiry, deepened the conceptual understanding of the students in relation to the light-matter interaction and other events that occurred following the decrease in the intensity of light entering the eye, caused by the reduced pressure in the vacuum bell jar.

A pair of galvo mirrors reflecting light from a laser pointer is suggested for use as a school demonstration of Lissajous figures. The device is small, cheap and easy to assemble. Combined with a two-channel waveform generator, a full spectrum of excellently stable Lissajous figures can be generated (concerning frequency ratio, amplitude ratio and initial phase angle difference). The operation at frequencies faster than the vision persistence allows us to draw the figures on a normal projection screen or on a wall. When operated with a violet laser pointer and a thermoluminescent foil, the frequencies can be decreased and the advance in figure drawing can be followed. The memory effect of the thermoluminescent foil also enables us to record and observe several Lissajous figures simultaneously.

Students often have difficulties comprehending situations in which wave characteristics of light are manifested. After teaching wave optics, we studied the level of understanding of reflective diffraction of light with a group of secondary school students, and the phenomenon of diffraction in general. We analysed the possibility of using convenient reflexive diffraction gratings (compact discs and rulers with millimetre and half-millimetre markings) using suitable research school experiments which can be prepared. With appropriate methods of visualising the superposition of light waves, those experiments represent the basis for an appropriate conceptual change in the understanding the diffraction of light.

Comprehension of the 3D structure of objects usually represented in 2D is a critical part of understanding molecular geometries. The frequency with which students actually get hands-on with 3D molecular structures is often limited to a singular laboratory session. We sought to develop a set of molecular shapes that were inexpensive enough not only to deploy in a first-year laboratory setting but also to allow the students to take the set home with them to study at their leisure. Laser-cut acrylic parts in five colors were used, and each set could be quickly assembled into the 13 different molecular shapes commonly encountered at the first-year level. The set of shapes was attractive, useful, and easy and fast to fabricate, and they were appreciated by our students. All files have been released in an open-source format, so any interested parties can deploy these models as soon as they secure access to a suitable laser cutter.

We have developed a laboratory project in which students prepare liposomes, expose them to hyperosmotic and hypoosmotic solutions, and follow the resulting shrinking and swelling (respectively) with laser light scattering. Each light intensity transient can be fit to an exponential decline or rise, with the decay constant (k) and the amplitude ([Delta]V[subscript max]) being indirectly related to the kinetics and thermodynamics (respectively) of transmembrane osmotic flux. Students vary the experimental system by changing the types and concentrations of osmolytes such as alcohols, amides, and salts. Students then compare how these changes alter the rate and extent of osmotic flux. This upper division biochemistry laboratory project is a challenging and rewarding one that exposes students to a biomolecule (lipid) and a spectroscopic technique (laser spectroscopy) that are not commonly used in the undergraduate laboratory setting.

Laser engravers/cutters have found their way into many technology and engineering (T&E) education laboratories. Their use can range from from cutting balsa wood truss designs to embossing a decorative logo on a student's project, and the range of materials can be almost as broad. While their capabilities can be virtually endless and the machine may seem relatively safe, there are some key guidelines to keep in mind when it comes to operating a laser engraver/cutter safely. Among these are: (1) read and understand the owner's manual to reduce the risk of damaging the machine, ruining the material, and most importantly, the risk of injury; (2) institute clear and consistent safety procedures just like any other piece of equipment in a T&E lab; and (3) use appropriate materials and adjust the machine to the correct settings for safer laser engraver/cutter operation. This "Safety Spotlight" provides further guidance on general laser engraver/cutter safety and material safety. It concludes with a list of helpful resources.

In this paper of I have reviewed the test done for validating the special theory of relativity using masers and lasers in last one century. Michelson-Morley did the first experimental verification for the isotropy of space for the propagation of light in 1887. It has an accuracy of 1/100th of a fringe shift. The predicted fringe shift on the basis of propagation of light through ether was 0.4 but Michelson-Morley did not observe any fringe shift and came up with a negative result. Their experiment was repeated with modern and more sophisticated versions using highly monochromatic masers and lasers which have kept any ether drag to the limit of < 1/1000th of the earth's orbital velocity and validated the isotropy of the space to the extraordinary limit of one part in 10[superscript15] . The necessary discussion on masers, lasers, its properties and applications with brief definition of beats is also given in this paper for the completeness of the discussion apart of the experimental method for validating the constant speed of light in different directions using masers and lasers.

This paper explores the pedagogy underpinning the use of laser manufacturing methods for the teaching of science, technology, engineering and mathematics (STEM) at key stage 3 design and technology. Clock making (horology) has been a popular project in design and technology (D&T) found in many schools, typically it focuses on aesthetical design elements. This paper describes a new project, which has been developed to enhance the STEM content of a horology project through advanced utilisation of laser cutting machinery. It allows pupils to produce their own products from self-made mechanical timing mechanisms. The central aim is to strengthen the application of the underlying technology of mechanisms and the manufacturing capability of laser cutting technology in D&T. Trials with schools have shown success in gaining pupils' interest in STEM and provided feedback to improve the project. It has highlighted limits when delivering the engineering and maths content with teachers from non-technology backgrounds. The paper discusses this limitation through subject pedagogy, categorisation of teacher knowledge, and teaching effectiveness through experiential and problem-based learning approaches.

In a university third-year instrumental chemistry laboratory students build a laser based polarimeter for determining light scattering with commercially available optical components used in modern optics research laboratories. During this laboratory experiment, students learn that solutions containing molecules which scatter light also influence the polarization properties of the laser beam by measuring Stokes parameters to calculate the degree of linearly polarized light. They also discover how the polarization properties of a laser beam are affected by half- and quarter-wave plates. Lastly, students are asked to recognize and assess the sources of error associated with the experiment including background intensity, integration time, and polarizer angle accuracy when measuring the Stokes parameters. A majority of students who completed the experiment agreed that this laboratory experiment required more critical thinking than traditional building instrumentation modules that they were exposed to, and that it improved their ability to learn independently and perform research.

We describe a hands-on accurate demonstrator for cosmic rays realized by six high school students. The main aim is to show the relevance and the functioning of the principal parts of a cosmic ray telescope (muon detector), with the help of two large sized wooden artefacts. The first one points out how cosmic rays can be tracked in a muon telescope, while the other one shows the key avalanche process of electronic ionization that effectively allows muon detection through a photomultiplier. Incoming cosmic rays are visualized in terms of laser beams, whose 3D trajectory is highlighted by turning on LEDs on two orthogonal matrices. Instead the avalanche ionization process is demonstrated through the avalanche falling off glass marbles on an inclined plane, finally turning on a LED. A pictured poster accompanying the demonstrator is as effective in assisting cosmic ray demonstration and its detection. The success of the demonstrator has been fully proven by the general public during a science festival, in which the corresponding project won the Honorable Mention in a dedicated competition.

A low-cost time-resolved emission spectrometer optimized for ruby emission is presented. The use of a Class II diode laser module as the excitation source reduces costs and hazards. The design presented here can facilitate the inclusion of time-resolved emission spectroscopy with laser excitation sources in the undergraduate laboratory curriculum. The ruby decay data show evidence of radiation trapping, an interesting optical phenomenon discussed in the research literature.

Fluorescence spectra excited by laser pointers have been the subject of several papers in "TPT". These papers all describe a fluorescence phenomenon in which the reflected laser light undergoes a change in color: this color change results from the combination of some partially reflected laser light and additional colors generated by fluorescent emission. Here we examine the fluorescence spectra of highlighter inks using green and violet laser pointers. We use an RSpec Explorer spectrometer to obtain spectra and compare the emission spectra of blue, green, yellow, orange, pink, and purple highlighters. The website Compound Interest details the chemical composition of highlighter inks; in addition, the site discusses how some base dye colors can be combined to produce the variety commercially available colors. Spectra obtained in this study were qualitatively consistent with the Compound Interest site. We discuss similarities and differences between various highlighter colors and conclude with the relevance of such studies to physics students.

This laboratory introduces students to laser-induced breakdown spectroscopy (LIBS) for the analysis of metals in soil and rock samples. LIBS employs a laser-initiated spark to induce electronic excitation of metal atoms. Ensuing atomic emission allows for qualitative and semiquantitative analysis. The students use LIBS to analyze a series of standard samples that contain various elements and construct a table of emission line wavelengths for each element analyzed. Students then identify metals in various soil and rock samples. Students gain valuable experience in qualitative analysis using an important spectroscopic tool, while gaining hands-on experience with a spectrometer employing a high energy laser pulse as an excitation source. The LIBS spectrometer is applicable to upper and lower division chemistry courses and can be used as an effective demonstration tool for students in 5th to 12th grade.

This column provides background science information for elementary teachers. This month's issue discusses the science behind self-driving cars, but first explains how a car "with" a driver works.

A simple diffraction experiment was designed using banana stem as natural grating. Coherent beams of lasers with wavelengths of 632.8 nm and 532 nm that pass through banana stem produce periodic diffraction patterns on a screen. The diffraction experiments were able to measure the distances between the slit of the banana stem, i.e. d = (28.76 ± 0.295) × 10[superscript -6] for a laser with a wavelength of 632.8 nm and d = (26.62 ± 0.002) x 10[superscript -6] for a wavelength of 532 nm. Therefore, banana stem could be used as an easily obtained and low cost grating for diffraction experiments.

The lifetimes of the photoluminescent compounds contained in the coating of fluorescent compact lamps are usually measured using specialised instruments, including pulsed lasers and/or spectrofluorometers. Here we discuss how some low cost apparatuses, based on the use of either sensors for the educational lab or commercial digital photo cameras, can be employed to the same aim. The experiments do not require that luminescent phosphors are hazardously extracted from the compact fluorescent lamp, that also contains mercury. We obtain lifetime measurements for specific fluorescent elements of the bulb coating, in good agreement with the known values. We also address the physical mechanisms on which fluorescence lamps are based in a simplified way, suitable for undergraduate students; and we discuss in detail the physics of the lamp switch-off by analysing the time dependent spectrum, measured through a commercial fiber-optic spectrometer. Since the experiment is not hazardous in any way, requires a simple setup up with instruments which are commonly found in educational labs, and focuses on the typical features of the exponential decay, it is suitable for being performed in the undergraduate laboratory.

We investigate students' sense of ownership of multiweek final projects in an upper-division optics lab course. Using a multiple case study approach, we describe three student projects in detail. Within-case analyses focused on identifying key issues in each project, and constructing chronological descriptions of those events. Cross-case analysis focused on identifying emergent themes with respect to five dimensions of project ownership: student agency, instructor mentorship, peer collaboration, interest and value, and affective responses. Our within- and cross-case analyses yielded three major findings. First, coupling division of labor with collective brainstorming can help balance student agency, instructor mentorship, and peer collaboration. Second, students' interest in the project and perceptions of its value can increase over time; initial student interest in the project topic is not a necessary condition for student ownership of the project. Third, student ownership is characterized by a wide range of emotions that fluctuate as students alternate between extended periods of struggle and moments of success while working on their projects. These findings not only extend the literature on student ownership into a new educational domain--namely, upper-division physics labs--they also have concrete implications for the design of experimental physics projects in courses for which student ownership is a desired learning outcome. We describe the course and projects in sufficient detail that others can adapt our results to their particular contexts.