Propagation of polarized mechanical waves in an anisotropic medium Sergej Faletiˇ c 1 , Mojca ˇ Cepiˇ c 2,3 1 University of Ljubljana, Faculty of Mathematics and Physics, Jadranska ulica 19, 1000 Ljubljana, Slovenia 2 University of Ljubljana, Faculty of Education, Kardeljeva ploˇ sˇ cad 16, 1000 Ljubljana, Slovenia 3 Institute Joˇ zef Stefan, Jamova 39, 1000 Ljubljana, Slovenia E-mail: sergej.faletic@fmf.uni-lj.si Abstract. During the propagation in an anisotropic medium, linearly polarized light in general becomes elliptically polarized. One can detect the polarization state of the transmitted light, but not the evolution of the polarization state during the propagation inside the material. We present a mechanical model where this evolution can be observed. The anisotropic medium is modelled by a series of coupled anisotropic oscillators. An oscillator consists of a bead hanging on an elastic string, and is coupled to neighbouring oscillators with stronger springs. When the system is excited in the plane perpendicular to the springs, the trajectories of the oscillating beads indicate the polarization state of the excitation at their respective positions. We analyze the model analytically, numerically and experimentally. 1. Introduction Understanding of polarized light propagation inside an anisotropic medium is difficult even for good physics students [1]. It is common practice in teaching physics to discuss waves and polarization first on mechanical systems, usually strings, before extending the concepts to electromagnetic waves. Direct observations of mechanical systems provide an experiential basis for the construction of mental models. It is also in line with a constructivistic approach to physics teaching, which emphasizes progress from the known to the unknown. However, an extensive literature search yielded no reports on real-life mechanical wave propagation in anisotropic media. Providing a mechanical system, which exhibits the discussed behaviour, appears to be a missing link in the teaching chain. The experiment described herein can be used as an observation experiment for building new knowledge or as a testing experiment for testing the result of the mathematical model. In both cases it offers support for active learning. But, it can also be used as a demonstration experiment in a traditional setting. An anisotropic medium in general does not preserve the polarization state of a propagating wave. Inside an anisotropic material, a wave propagates as two waves Page 1 of 11 AUTHOR SUBMITTED MANUSCRIPT - EJP-103329.R1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 This is an author-created, un-copyedited version of an article published in European journal of physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6404/aab12e