A research-based educational path on diffraction of light was designed for upper secondary schools. Through the experimental exploration of the diffraction pattern produced by a laser beam incident on a single slit, students first analyse the diffraction pattern qualitatively, recognizing the global properties, then measuring with on-line sensors the light intensity vs position, constructing empirical relations between order and position of minimum, order and position of maximum, position and intensity of maximum. Making a wave hypothesis on the nature of light, a computer model based on Huygens' principle takes into account the intensity pattern of light. Experiments in school were performed with students, using inquiry based learning tutorial worksheets e pre-Test, post-Test. Positive learning indications of students emerged concerning the role of diffraction in everyday situations, and the general features of the diffraction pattern. The findings suggests that to produce an effective change in the model of light, students need to reflect extensively in the hypothesis at the base of their prevision and to by involved in deep in a modelling activity.
