Light propagation and visual patterns: Preinstruction learners' conceptions

Abstract

This study formed part of a project aimed at revising the instructional approach for geometrical optics in the 10th grade. The instructional intervention was based on the extensive use of a diagrammatic representation as a descriptive, explanatory, and problem-solving tool in the domain. The purpose of this study was to elicit the conceptions and representations of light propagation, image formation, and sight typical to preinstruction learners, with special attention to identifying precursors of problematic features of postinstruction students' knowledge. The premise for this study was that the difficulties students have before, during, and after traditional instruction with respect to representing optical phenomena have their origins in the fragmented prescientific knowledge constructed on the basis of experience. We believe that the difficulties persist because the key factors leading to fragmentation are not usually addressed and remedied. The main findings of the study indicate that (a) preinstruction students display some familiarity with optical systems, light propagation, and illumination patterns; (b) student-generated graphical representations describing and explaining optical phenomena display some features of formal ray tracing; (c) preinstruction students have not developed a consistent descriptive and explanatory model for light propagation; and (d) the context of sight seems to have a confounding effect on the establishment of a unified prior model for optical phenomena.

Primary Trainee Teachers’ Learning and Teaching About Light: Some pedagogic implications for initial teacher training

“…It is intuitive to spontaneously explain phenomena in terms of cause and effect where ideas are guided by common sense experience, and this can be particularly misleading in optics (Galili & Hazon, 2000). Understanding formal explanations of how optical phenomena occur involves the learner in synthesizing knowledge concerning light propagation, illumination pattern and the observer's visual pattern (Langley et al, 1997).…”

The Properties and the Nature of Light: The Study of Newton’s Work and the Teaching of Optics

“…However, the evidence suggests that there are appropriate ways to introduce initially students to the key idea of light in a way that allows them to solidify their conception of it as a physical something that moves in space (Fetherstonhaugh & Treagust 1992;Goldberg & McDermott 1986, 1987Langley et al 1997). This can be utilised by teachers to teach the phenomenon of light using the ray model, that is, to teach students the geometrical model of light, especially in ages at which students are not at the appropriate developmental level to think about the wave or the particle model of the nature of light.…”

“…It would not be hard to trace many common themes between these conditions and Lakatos ' (1973) conditions that a theory must fulfil in order to supersede another theory, as we discussed in Section 1. Langley et al (1997) report similar results with older students and claim that the formal model for geometrical optics ''does not evolve through chronological maturation by the refinement of adolescent prescientific notions;'' school intervention must step in (Langley et al 1997, p. 418). Prior to any instruction students have formed various models in their effort to make sense of their experiences with the phenomena of light and sight.…”

“…Students that have taken the relevant courses usually fail to explain even the simplest phenomena of light propagation by drawing the appropriate rays of light and relating them to the source and the objects with which the light interacts (Andersson & Karrqvist 1983;Feher & Rice 1988;Fetherstonhaugh & Treagust 1992;Langley et al 1997). Furthermore, it seems as though the reliance on the geometrical model hinders subsequent efforts to teach students phenomena, such as diffraction and interference, whose explanation requires the consideration of light as a wave (Colin & Viennot 2000;Wosilait et al 1999).…”

Teaching Image Formation by Extended Light Sources: The Use of a Model Derived from the History of Science

“…In the research field of Science Education and in the domain of optics in particular, the vast majority of studies conducted on children's representations concerning light phenomena assumes dimensionless light sources, that is, point sources (Andersson and Kärrqvist 1983;Boyes and Stanisstreet 1991;Eaton et al 1984;Guesne 1978;Hosson and Kaminski 2002;Langley et al 1997;Palacios et al 1989;Ramadas and Driver 1989;Selley 1996). However, since the chapters taught on optics include topics whose understanding requires the use of extended light sources (that is, pinhole images, shadow formation, mirror images, mechanism of vision, lens and prism images), this has led to the development of a (limited) number of research initiatives based on this latter assumption.…”