From one slit to diffraction grating: optical physics lab by means of computer on-line sensors

Abstract

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 (Gervasio & Michelini 2009). Data can be exported in text format and data fitting can be done by means of a spreadsheet. The educational proposal about single-slit diffraction (Corni et al. 1993) has been tested with 114 students (aged 18-19) in 2008 and 2014. Many of these interventions were research-based educational path. Data concerning learning processes of 29 students are described in (Michelini & Stefanel 2015). We are now developing an educational path about optical spectroscopy for upper secondary-school and university students, and the need to extend the educational proposal to the case of diffraction from a diffraction grating has emerged: this is necessary in order to deal with lab activities involving the analysis of spectra and to study the conceptual knots emerged in the literature in the case of optical spectra generated by a prism (Ivanjek et al. 2015a, 2015b). 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 (Santi et al. 1993). The proposed IBL path based on the exploration of the multiple slit diffraction pattern has been used with 98 upper secondary school Italian students and 56 freshmen in biotechnology sampled from University of Udine. Data has been analyzed and the results are under discussion. This poster shows the experimental activity proposed to the students and its characteristics.