LIGHT-PROPAGATION AND VISUAL-PATTERNS - PREINSTRUCTION LEARNERS CONCEPTIONS

This study formed part of a project aimed at revising the instructiona l approach for geometrical optics in the 10th grade. The instructional intervention was based on the extensive use of a diagrammatic represe ntation as a descriptive, explanatory, and problem-solving tool in the domain. The purpose of this study was to elicit the conceptions and r epresentations of light propagation, image formation, and sight typica l to preinstruction learners, with special attention to identifying pr ecursors of problematic features of postinstruction students' knowledg e. The premise for this study was that the difficulties students have before, during, and after traditional instruction with respect to repr esenting optical phenomena have their origins in the fragmented presci entific knowledge constructed on the basis of experience. We believe t hat the difficulties persist because the key factors leading to fragme ntation are not usually addressed and remedied. The main findings of t he study indicate that (a) preinstruction students display some famili arity with optical systems, light propagation, and illumination patter ns; (b) student-generated graphical representations describing and exp laining optical phenomena display some features of formal ray tracing; (c) preinstruction students have not developed a consistent descripti ve and explanatory model for light propagation; and (d) the context of sight seems to have a confounding effect on the establishment of a un ified prior model for optical phenomena.