Bulletin of the American Physical Society
2013 Annual Fall Meeting of the APS New England Section
Volume 58, Number 11
Friday–Saturday, October 11–12, 2013; Bridgewater, Massachusetts
Session D2: Parallel Session: Physics Education, Light & Devices |
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Chair: Tom Kling, Bridgewater State University Room: Mathematics and Science Auditorium CON 122 |
Saturday, October 12, 2013 8:00AM - 8:12AM |
D2.00001: Teaching Fluids to Life Science Students Dawn Meredith, Daniel Young, James Vesenka, Katherine Misaiko, Elizabeth Whitmore There is consensus nationwide that typical current introductory physics course for life science students (IPLS) is not meeting their needs. We have been rethinking the IPLS for several years, and our focus in the past few years has been on developing curricula for static and moving fluids, a challenging yet essential topic for biologist. Our approach has been to couple a molecular point of view with forces perspective to provide students the tools to reason mechanistically about fluids. We will share our curricular materials and our data which give evidence that this approach does improve student understanding. [Preview Abstract] |
Saturday, October 12, 2013 8:12AM - 8:24AM |
D2.00002: Group Problem Solving Sessions (GPS) and WikiSpaces (WikiS) in Physics Classrooms Hashini Mohottala We report the combine use of Wikispaces and Group Problem Solving sessions conducted in the introductory level physics classes. This method gradually evolved from the combine use of Wikis and Just in Time Teaching (JiTT) practiced over the past years. As a part of this new method, some essay type problems, parallel to the chapter in discussion, were posted on the Wikis in weekly basis and students were encouraged to visit the pages and do the work without providing numerical final answers but the steps. At the end of each week students were further evaluated on problem solving skills opening up more opportunity for peer interaction through GPS. A class of 30 students was divided into 6 groups and each group was given one problem to solve. The problem numbers are drawn in a raffle and the answers were graded. Students developed a set of skills in decision-making, problem solving, communication, negotiation, critical and independent thinking and teamwork through the combination of WikiS and GPS. In addition, we find it as an extremely useful tool to reach students when teaching a hard science subject like physics as it makes learning the subject very stimulating, motivating, engaging and most importantly, fun. [Preview Abstract] |
Saturday, October 12, 2013 8:24AM - 8:36AM |
D2.00003: Scientific Understanding: Issues of Fact and of Method in Undergraduate Physics Education - A Critical-Thinking Approach to Analyzing some of the Science while Teaching the Scientific Method Laurence I. Gould Undergraduates tend to learn and enjoy physics through its well-established corpus (mechanics, electricity and magnetism, quantum theory, etc.). However, there is a relatively new opportunity to enhance the learning of physics through critical thinking in a non-traditional area. Such thinking can be fostered through an analysis of both the science and methodology involved in the area commonly known as ``global warming/climate change'' (AGW). This opportunity arises because of an increasing number of scientists from around the world who have been examining and challenging [1] what is said to be the ``consensus'' claim that dangerous AGW is caused primarily by human-produced carbon dioxide. This talk will include how such critical thinking works through: (1) two independent-study courses I have done with some physics majors, and (2) a college-wide freshman seminar about AGW (which may encourage students to consider taking more physics courses or even take physics as a Minor or Major). Audience participation will be encouraged if there is time.\\[4pt] [1] The 2011 Interim Report from the Nongovernmental International Panel on Climate Change http://www.nipccreport.org/reports/2011/2011report.html (most of the research reported here appears in peer-reviewed science journals) [Preview Abstract] |
Saturday, October 12, 2013 8:36AM - 8:48AM |
D2.00004: White-light supercontinuum generation via filamentation in SF$_6$ with low threshold and stable pointing Hui Chen, Vincent Tagliamonti, George Gibson White-light supercontinuum generation via filamentation is discussed in a gaseous medium-SF$_6$. With a pressure of 1 atm, a filament is formed with 0.35 mJ, 50 fs pulses. The dependence on pressure, input laser energy and laser repetition rate of the filament is discussed. Furthermore, the spatial chirp in the presence of spectral broadening with and without the filament is compared. This is the lowest threshold for broad continuum generation, to our knowledge, and the pointing stability of the filament is similar to that of the original laser beam. The pulse is recompressed by a pair of chirped mirrors and a pulse duration of 14.6 fs is obtained. [Preview Abstract] |
Saturday, October 12, 2013 8:48AM - 9:00AM |
D2.00005: Non-conventional white light emission of Al$_{2}$O$_{3}$ induced by laser diode excitation Joseph Liguori, Gokhan Bilir, Gonul Ozen, Baldassare Di Bartolo We discovered broadband yellowish white light emission from commercially obtained nominally un-doped $\gamma $-Al$_{2}$O$_{3}$ nano-powders with a crystalline size of less than 50 nm. This emission was obtained under 975 nm laser diode excitation. We measured the spectrum, decay time, and rise time of this white light under a variety of conditions, such as various environment pressures, temperatures, pumping powers and pumping wavelengths. We also studied the decay- and rise times of various wavelengths within the emission spectrum. The white light spectrum was ranged from 450 to 950 nm. Its intensity was not dependent on the temperature of the samples, but was strongly dependent on pressure, with higher values at low pressure. It was also dependent on pumping laser power. [Preview Abstract] |
Saturday, October 12, 2013 9:00AM - 9:12AM |
D2.00006: Very high transmittance, back-illuminated, silicon-on-sapphire universal substrate for high energy conversion efficiency photovoltaic device applications Alvin G. Stern There is a growing need for a universal solution that allows the air mass (AM) 1.5 solar irradiance spectrum having a broad wavelength range from the ultraviolet to the midwave infrared between 280-4000 nm, to be transmitted with very high efficiency approaching 100 percent into silicon to support the development of high energy conversion efficiency photovoltaic (PV) devices. Due to the high costs of back-illuminating light detectors, needed for achieving high quantum efficiency in devices, most commercial silicon PV panels are at present front-illuminated and as a result attain module efficiencies of only 15 percent whereas the maximum energy conversion efficiency using silicon single junction PV devices could be as high as 30 percent. We have designed a novel, very high transmittance, back-illuminated silicon-on-sapphire (SOS) substrate that enables 93.7 percent of the full AM 1.5 solar irradiance spectrum to be transmitted into the silicon semiconductor layer to enable PV light detectors that could also include advanced, multijunction, bandgap engineered device architectures, to operate at their maximum theoretical limits of efficiency. Fabrication of the novel substrate presents a unique set of challenges that we are endeavoring to overcome. [Preview Abstract] |
Saturday, October 12, 2013 9:12AM - 9:24AM |
D2.00007: Frequency dependence property of photoelectric effect for introductory undergraduate lab course Chandra Yelleswarapu Three empirical laws defines photoelectric emission: a) for a given material there is a minimum (or threshold) frequency of the incident light below which no photoelectrons will be emitted; b) the maximum kinetic energy of the emitted electrons is proportional to the frequency of the incident light; and c) the number of electrons ejected from an illuminated surface per unit time, i.e., the photoelectric current, is proportional to the intensity of the incident light (given that the frequency is above the threshold). Since the 1960's, majority of the focus has vested in improving the sources -- starting from a mercury arc lamp to employing light emitting diodes (LEDs) in more recent times. These developments made photoelectric effect experiment simple and has become standard in introductory undergraduate laboratory courses. However a different and equally important aspect of photoelectric effect is threshold frequency dependence. For a given material, there is a minimum frequency of incident light needed below which no photoelectrons are emitted even if the light source is very intense. This property of photoelectric effect is not easy to conceptualize for undergraduate students and is difficult to validate in an undergraduate physics laboratory. Here we demonstrate this property using red, green and blue ordinary light emitting diodes (LED) as sources as well as detectors. Furthermore this experiment is cost-effective as each LED costs less than 50 cents. [Preview Abstract] |
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