A potentially thought-provoking didactic experiment involving light reflection in an apparently mysterious case

A didactic experiment involving concepts and laws of optics (e.g., Brewster angle, Fresnel equations, polarization) is inserted in an activity focusing on the scientific modeling process designed for laboratory classes in an undergraduate Physics course. The activity is motivated by a problem that involves an apparent mystery related to the disappearance of an object in the dephts of a crystal clear lake. To unravel the apparent mystery, it is suggested that the reflection and transmission of sunlight across the lake’s surface has a determining role in explaining the phenomenon. A theoretical model is then built and evaluated by means of an experiment in which a laser light, polarized in the parallel and perpendicular direction to the plane of incidence, is reflected on the surface of water contained in a vat. It is shown that this model is capable of predicting the disappearance, during the afternoon, of a coin contained in a vessel with a little water and illumintated by sunlight. We understand that this article contributes to the teaching of Physics, as it brings an activity that promotes the connection between theoretical and practical knowledge from a potentially exciting problem, aiding students to build meaning from scientific knowledge and understand central elements of the experimental work from the perspective of scientific modeling.

Keywords
Fresnel equations; polarization of light; scientific modeling; experimental activities; didactic laboratory