Didactic procedure for teaching Planck's formula in Engineering majors

Abstract

This article proposes a didactic procedure for teaching Planck's formula in engineering majors, following the cyclic sequence: Initial facts ? Model-hypothesis ? Logical consequences ? Experimental verification. The essential elements of the quantization of energy are analyzed, with historical notes that facilitate the understanding of the phenomenon of thermal radiation, and the role that scientists played in its explanation. Initial facts in the exemplified cycle are considered, the laws of Kirchhoff, Stefan-Boltzmann and Wien, in addition to the Rayleigh-Jeans formula, and the fundamental approaches that allowed Planck to propose his hypothesis to find the theoretical solution to distribution are specified of energy in the spectrum of black body radiation, which culminates in 1900 with the proposal of the quantum of action, expressed by the universal constant h that bears his name. Once Planck's formula has been obtained, the facts that served as the basis, as particular cases, are deduced from it as logical consequences, and other relationships of importance for physics and chemistry are obtained. To close the cycle, the experimental verification is performed, taking as an empirical fact the measurement of cosmic background radiation, which behaves like the radiation of a black body at a temperature of 2.73 K. It concludes with examples of practical applications of thermal radiation, which involve some basic concepts of the theoretical elaboration of Planck: Solar energy, thermal covering and pyrometry.