Training teachers: explorative activities measuring Planck's constant

In recent years, Modern Physics has been included in the curricula of Italian secondary schools, so that many teachers are asking for specific didactical tools to allow their students to acquire the right skills to deal with final examinations. The Physics Department at University of Salerno (Italy) is, therefore, planning PLS (Piano Lauree Scientifiche / Scientific Degree Project) training courses to give some valid educational paths through new didactical strategies for Physics learning. Introducing quantum mechanics by experimental set-ups with commonly used materials is a rather interesting and challenging task. In fact, this practice allows teacher attending the course to reproduce the same experiments in their own class. Moreover, by using readily available material for the experimental set-up, a soft approach to Modern Physics can be achieved. In the present work, we propose the analysis of an experiment: the measurement of Planck's constant, one of the most important fundamental quantities in Modern Physics, by means of Light Emitting Diodes (LEDs). The properties of LEDs can be explained by means of elementary quantum mechanics concepts. As a consequence, when describing the quantum behaviour of these commonly used physical systems, Planck's constant needs to be considered. Therefore, to illustrate one possible way of measuring Planck's constant to high-school students, we can make use of the current-voltage (I-V) characteristics of a LED. In fact, by opportunely interpreting the measured I-V curves of these systems, by means of a linear fitting the value of Planck's constant can be obtained. (paper)