Using two models in optics: Students’ difficulties and suggestions for teaching

This paper focuses on difficulties linked to situations in physics involving two models: geometrical optics and wave optics. The starting point is an investigation of university-level students’ difficulties. Excerpts from textbooks are given, to illustrate potential difficulties. A content analysis is then presented, underlining two important features required for dealing with such situations: awareness of the status of the drawings, and the “backward selection” of paths of light. These features could provide some guidelines for the designing of innovative teaching strategies.