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Accurate measurements of refractive indices for dielectrics in an undergraduate optics laboratory for science and engineering students

Based on our novel method recently published in the Am. J. Phys. 77 337–43 (2009) for finding precise values of the indices of refraction for dielectrics from measurements of the polarized light reflected by the surface, in this paper we propose an improved technique for finding Brewster angles with a better precision, of 0.001°, using the same relative inexpensive optical equipment provided by the PASCO Scientific company and a simpler setup. The goal is to implement our procedure in a 3 h optics laboratory for undergraduate students using two different laser–dielectric systems. As compared to our previous work, now we eliminate the random fluctuations of the experimental time-dependent reflectance by controlling the irradiation time on the dielectric surface (and thus avoiding the overheating of the surface) and by using lasers which are stable during the data acquisition process. Also, in the present experiment, we use a computer-based filtering procedure of the experimental reflectance during the data acquisition process for increasing the precision of the measurements at any angle of incidence.