An investigation of student understanding of single-slit diffraction and double-slit interference

Results from an investigation of student understanding of physical optics i ndicate that university students who have studied this topic at the introdu ctory level and beyond often cannot account for the pattern produced on a s creen when light is incident on a single or double slit. Many do net know w hether to apply geometrical or physical optics to a given situation and may inappropriately combine elements of both. Some specific difficulties that were identified for single and double slits proved to be sufficiently serio us to preclude students from acquiring even a qualitative understanding of the wave model for light. In addition, we found that students in advanced c ourses often had mistaken beliefs about photons, which they incorporated in to their interpretation of the wave model for matter. A major objective of this investigation was to build a research base fur the design of a curricu lum to help students develop a functional understanding of introductory opt ics. (C) 1999 American Association of Physics Teachers.