Schematic drawing of a single glass bead hosting one internal specular reflection at the backside interface.|@|~(^,^)~|@|Correlation between a and θ plotted for differing refractive index of a glass sphere.|@|~(^,^)~|@|Correlation between θ and I_r for different n of a glass sphere.|@|~(^,^)~|@|Normalized R_A values plotted as a function of n of a glass sphere for different ranges of observation angle. Here, observation angle denotes the angle between the optical axis and the direction in which the photodetector in the instrument deployed in this study is located. Note that the minimum observation angle of the instrument is 0.2°, and the active area of the photodetector in the instrument corresponds to an angle range of 0.05°, so that we introduce an uncertainty of 0.05° for each observation angle under consideration.|@|~(^,^)~|@|Comparison of calculated and measured R_A values. The observation angle is fixed to 0.2 ± 0.05° in this plot. Refer to Table 1 for the letters indicating the glass-bead batches. Note that glass-bead batch K is not presented, because its refractive index is unknown.

Current Optics and Photonics 2019;3:415~422 https://doi.org/10.3807/COPP.2019.3.5.415