The refractive index is a measure of how much light bends or refracts when it enters a material. Mathematically, it's defined as the ratio of the speed of light in a vacuum to the speed of light in the material. Different materials have different refractive indices, which can influence phenomena like reflection, refraction, and dispersion of light. Total internal reflection is a when a light ray traveling through a medium strikes the boundary with another medium at an angle greater than the crit