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Analysis of the Experiment of Light Polarization

In the experiment of college physics, quarter wave plate is often used to study the circularly and elliptically polarized light. However, most students cannot get circularly polarized light in the experiment. Two possible causes of this phenomenon are analyzed, thus, the thickness error of the quarter wave plate and the incident angle not being 0 degree at the plate surface. By comparing the theoretical and experimental results, we conclude that the main error comes from the thickness error of the plate. By investigating the cases of normal incidence and oblique incidence on the plate, the intensity distributions of the emergent light are obtained, as well as the relations between the thickness of the plate and the intensity distributions. Based on these relations, two methods to measure the thickness of the plate are proposed, and the phase difference between ordinary and extraordinary lights can be set precisely by rotating the plate around its optical axis.