Simetria e propriedades ópticas dos materiais: entendendo a atividade óptica

Abstract

The present study relates the symmetry of the crystallographic structure and the optical properties of the materials, presenting as general objective a survey of the conceptual difficulties presented by the students when constructing the concept of Symmetry as well as establishing its relation with the optical properties of the materials. For that, a Didactic Sequence (SD) was elaborated, using collaborative and investigative activities, focused on the experimental observation of the optical activity in sucrose solutions. SD approached the Neuman Principle, which is a postulate of Condensed Matter Physics, which states that the physical properties of a material medium manifest in the Symmetry properties of the medium itself. Its fundamental consequence is that we can gather information about the crystallographic structure by analyzing the physical properties of the medium. The qualitative research methodology was used as data analysis methodology and as teaching strategy the active methodology, especially research teaching. The SD initially proposes an investigation on the concept of Symmetry and their respective operations. A strategy was sought in which the student could construct the concepts of Symmetry and Symmetry operations throughout the activities. Then the concept of polarized light was introduced, with experiments that provided a conceptual approach. After this step, the experimental theoretical study of the optical activity was started. Initially the conditions of symmetry were approached for optical activity to manifest. According to the Neuman Principle, the physical properties of a material must be invariant to the symmetry operations of its crystalline structure. SD was concluded with an experimental activity to determine the specific rotation of sucrose and its comparison with data in the literature. From the study carried out, it was possible to perceive that the use of collaborative and investigative activities in the present research, provide the conditions for the students to construct and differentiate the chemical and physical concepts involved in the analysis of the optical activity, physical property. In addition, since this topic involves Material Physics and the historical inter-relations between Physics and Chemistry, the proposal was able to provide a teaching and learning environment involving an interdisciplinary proposal for High School.