The effect of the thickness of the glass plate of a hollow prism on the accuracy of measuring the refractive index of edible oil

Effect of the thickness of the ordinary commercial glass plate utilized for making hollow prism on accuracy of measuring the refractive index of edible oil was investigated. The edible oil sample was filled into the prism cavity and then a laser beam (helium neon, He–Ne) is passed through the prism cavity. The prism angle and the deviation angle of the refracted laser beam is used for calculation the refractive index. The thickness of the glass plate used to make hollow prisms was varied from 2 mm to 5 mm. The effect of the glass plate thickness to measurement accuracy was examined using the fluid prisms with different prism angles of 30°, 45° and 60°, respectively. It was discovered that refractive index of edible oils can accurately be determined by employing the hollow prisms constructed from the ordinary commercial glass plate. It was also found that the thickness of the glass plates utilized for constructing the hollow prism significantly influences the measured refractive index, namely the refractive index increases with increasing thickness of the glass plate. This implies that the glass plate thickness constitutes the measurement accuracy. The commercial glass plate thickness giving to the highest measurement accuracy is 2 mm.