Optical physics is part of many national curricula, but is usually treated in a reductive and not useful way for students learning. A wide research literature point out that many students do not have clear the features of the phenomena considered, have difficulties in applying the maxima/minima condition to solve also simple problem of interference, apply reasoning based on the rays and rectilinear propagation or models mixing optical and geometrical optics. To overcome these learning problems, different research groups proposed new educational approaches and the use of on-line sensors opened new opportunities for learning in this field. The PERG of the University of Udine studied how to exploit the potentiality of new technologies in teaching optical diffraction, aiming to enable students to acquire a complete vision of optical diffraction and to build a functional understanding of the wave nature of light and the wave model of light behavior. Researches was performed to explore how students analyze the phenomenology and pass from a geometrical description of light behavior, to a wave model. The students conceptions on light diffraction, their learning path and their learning progression were monitored using inquiry based learning open tutorials, audio recording of teaching/learning sessions with students. The qualitative analysis of the monitoring tools showed that students developed different models when they faced a phenomenology far from their everyday experience as that of the light diffraction one. Many students developed models based on a geometrical rectilinear path light propagation to account the phenomenology they observed. The in depth analysis of phenomenology produce an adaptation of student models able to describe some features of the phenomenology, but not to interpret it.
