This study outlines ongoing research within the area of physics education, namely the investigation of the relationship between conceptual understanding and quantitative problem-solving. Industry, society and research need graduates to be excellent problem solvers with an ability to conceptualise and transfer their understanding and knowledge. However recent research has shown that physics students are not developing the conceptual understanding necessary to become adept problem-solvers. Physics education tends to rely on the assumption that students will develop an understanding of the conceptual nature of physics by solving quantitative problems. Research has shown that this is not the case and students cannot develop as problem-solvers without first having the conceptual understanding. Many of these physics graduates go on to work in optics, in areas such as nanotechnology, photonics fabrication and optical sensing. This research involves an investigation of student learning in physics and the impact this has on conceptual understanding and their ability to solve quantitative and qualitative problems. It builds on research carried out in the United States in order to obtain a better understanding of how students learn physics and the difficulties they have developing an understanding of the conceptual nature of physics. It aims to develop a systematic way of identifying students’ misconceptions in physics and to assess the affect these have on student learning and the development of understanding. This research will inform teaching and assessment practices, not only in physics education but also in other disciplines so that third level education can produce better problem-solvers for industry, research and a knowledge-based society.
The Hilger & Watts gauge-block interferometer was designed and manufactured commercially in the 1950s. The instrument uses isotope lamps as wavelength standards to perform absolute length calibration of gauge blocks (slip gauges) up to 100 mm in length, to an accuracy of approximately 1 ppm. It is entirely manually operated. In order to make the instrument more suitable for the modern laboratory, new hardware has been added, and a customized software package developed to automate the measurement process. This paper shows how interferograms may be imaged successfully at each of the eight available wavelengths, and the critical fringe fraction measurement automated, ensuring an accuracy better than ±0.05 fringe. To demonstrate the validity of the new system, representative data are presented alongside data obtained using the traditional method and from an external accredited laboratory.
The use of electronic speckle pattern interferometry (ESPI) for non-destructive material characterization of thick and thin unplasticized polyvinylchloride (uPVC) pipes is presented. Pipes are tested by internal pressurization and ESPI gives a complete mapping of the resulting displacement field over the area imaged by the video camera. The results for the strain derived from ESPI data and from the standard mechanical method using strain gauges agree very well with each other. The interferometric method used is non-contact and gives high-confidence results for Young's modulus of uPVC pipes. The fringe counting method gives the total diplsacment over the field of view imaged by the CCD camera and is subject to a fringe error of 0.5. This simple approach is valid when the displacement behavior of the sample is known. When this is not the case then it is necessary to calculate the phase map of the displacement of digitally shifting the phase difference between the two beams in the interferometer. We have implemented this technique by modulating the laser diode drive current to alter the wavelength of the laser very slightly between frames. A linear phase map of the displacement is always obtained in the present case.
The available techniques for the study of high frequency vibration using electronic speckle pattern interferometry (ESPI) are briefly surveyed. We concentrate on two methods in particular. The first is a straightforward approach in which a CCD camera is used having a frame rate of at least twice the highest vibration frequency so that the sampling criterion is satisfied. The images are processed and analysed off-line. Digital phase shifting can be also implemented for detailed fringe analysis. The second approach is time-averaged ESPI in which the Bessel fringe function can be analysed in real time by modulating the optical path difference in the interferometer. This can be done either by using a vibrating component or, as in the present work, by direct modulation of the laser wavelength at the frequency of the vibrating mode.
In this paper a model for the implementation of a problem-based learning (PBL) course for a typical year physics one programme is described. Reference is made to how PBL has been implemented in relation to geometrical and physical optics. PBL derives from the theory that learning is an active process in which the learner constructs new knowledge on the basis of current knowledge, unlike traditional teaching practices in higher education, where the emphasis is on the transmission of factual knowledge. The course consists of a set of optics related real life problems that are carefully constructed to meet specified learning outcomes. The students, working in groups, encounter these problem-solving situations and are facilitated to produce a solution. The PBL course promotes student engagement in order to achieve higher levels of cognitive learning. Evaluation of the course indicates that the students adopt a deep learning approach and that they attain a thorough understanding of the subject instead of the superficial understanding associated with surface learning. The methodology also helps students to develop metacognitive skills. Another outcome of this teaching methodology is the development of key skills such as the ability to work in a group and to communicate, and present, information effectively.
Holographically recorded diffractive optical elements are described, which can be used to implement very simple self-aligning electronic speckle pattern interferometers (ESPI) and holographic interferometers requiring only a laser source and a CCD camera in the optical set-up. The ESPI systems can utilize transmission or reflection holographic optical elements (HOEs). The HOEs are essentially amplitude beamsplitters and recombiners whose recording and reconstruction parameters can be adjusted to optimize the ratio of reference and object beams reconstruction so as to maximize subtraction fringe contrast. The HOEs are recorded using a 4-component photopolymer system. In addition the HOEs can be recorded at visible wavelengths but used in ESPI systems, which incorporate at diode laser. The diode can be wavelength modulated. In this way we can incorporate digital speckle pattern interferometry (DSPI) or amplitude and phase modulation of the optical path difference for time-averaged speckle interferometry.
Optical interferometric techniques are being increasingly used in laboratory test and can usefully substitute other classical techniques when great accuracy in measuring displacement is required. In particular, Electronic Speckle Pattern Interferometry (ESPI) technique has aroused lively interest by the industrial and research users because does not require excessive environmental stability and does not necessary photo processing. In the paper the authors show the results obtained applying the ESPI methods to mechanical characterization of clay materials used to manufacture blocks for composite floors.
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