Refractive Index Determination of Rectangular Optical Slabs Using Modified Ray Tracing Method

Ubong Williams Robert, Department of Physics, Akwa Ibom State University, Ikot Akpaden, Mkpat Enin, Akwa Ibom State, NigeriaFollow
Sunday Edet Etuk, Department of Physics, University of Uyo, Uyo, Akwa Ibom State, NigeriaFollow
Okechukwu Ebuka Agbasi, Department of Physics, Federal University of Technology Ikot Abasi, Ikot Abasi, Akwa Ibom State, NigeriaFollow

Keywords

Measurement Uncertainty Analysis, Modified Ray Tracing Method (MRTM), Optical Characterisation Techniques, Optical Slabs, Refractive Index Determination

Document Type

Article

Abstract

The traditional ray tracing method (TRM) for determining the refractive index of optical materials is often time-consuming and poses challenges for individuals with visual impairments. Accurate refractive index determination is essential for selecting materials in optical instruments, optoelectronic devices, and optical communication systems. With the emergence of new materials, there is an increasing need for techniques that overcome the limitations of the TRM. In this study, a Modified Ray Tracing Method (MRTM) incorporating the use of a plane mirror to enhance image localisation and reduce alignment ambiguity was developed for determining the refractive indices of various optical materials, including soda, borosilicate, perspex, polystyrene, and acrylic slabs. The performance of the proposed method was evaluated through comparison with results obtained using a travelling microscope (considered the gold standard) and the conventional TRM under identical laboratory conditions. Statistical validation using Pearson Product Moment Correlation Coefficient (PPMCC), one-way ANOVA, percentage deviation analysis, and uncertainty assessment were included in the methodological framework to establish accuracy and reliability. The results demonstrated that the MRTM produced refractive index values with stronger agreement with the gold standard measurements, yielding a coefficient of determination (R² ≈ 0.998) and improved measurement consistency compared with the TRM. Furthermore, the MRTM achieved a measurement uncertainty of less than 2%, with repeatability of approximately 0.26% and reproducibility of approximately 0.22%, giving a combined value of about 0.34%, thereby satisfying established acceptance criteria for experimental testing methods. These outcomes indicate that the MRTM provides a cost-effective, reliable, and user-friendly alternative suitable for teaching laboratories and low-cost experimental environments where rapid and accurate refractive index determination is required.

Recommended Citation

Robert, Ubong Williams; Etuk, Sunday Edet; and Agbasi, Okechukwu Ebuka (2026) "Refractive Index Determination of Rectangular Optical Slabs Using Modified Ray Tracing Method," Engineering and Technology Journal: Vol. 44: Iss. 4, Article 3.
DOI: https://doi.org/10.30684/2412-0758.1560

DOI

10.30684/2412-0758.1560

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