Diffraction is a crucial phenomenon and its interpretation bridges from geometrical to wave optics and from wave optics to Quantum mechanics. Becoming familiar with the characteristics of the diffraction in the cases of one, two, many slits is an important experience for students not only from the subject point of view, but also on the methodological plan. The exploration of the relative interpretation by means of simulation and modelling offers to the students the opportunity to experience the typical methodological work in physics. An educational proposal was developed for the study of optical diffraction: from the analysis of a single slit diffraction, to a double slit and to a diffraction grating. It is based on a USB acquisition system designed and developed for experimental data acquisition in an educational lab, correlating position and light intensity measurements in one direction. Data can be exported in text format and data fitting can be done by means of an electronic sheet. The phenomenon laws obtained by data are interpreted under the wave nature of light by students and these laws are used for spectroscopic analysis of different light sources. Simulation software allows to build models of interpretation of phenomenology based on the first principles.
