Three Methods to Estimate the Refractive Index of a CD-ROM with a Smartphone

The refractive index (RI) is considered one of the most fundamental optical features of a sample, and estimating the RI, especially of a liquid, has become a popular topic in various STEM classes and events since it can help students to understand refraction conceptually.^1–5 However, the RI can be estimated not only by Snell’s law, but also by the critical angle of total reflection as well as Brewster’s angle, where the latter two cases can be viewed as special cases of the refraction with no refracted ray and no reflected ray, respectively. Therefore, this paper proposes three different approaches to estimating the refractive index of a sample with simple apparatus, corresponding to the three cases of refraction when light travels through different media, with the aim of helping students establish the connection of different optical phenomena and understand refraction more deeply. Considering the difficulty of preparing the experimental materials...