The refractive index unit (RIU) is a unit of measurement used in optics to quantify the amount of bending or refraction that occurs when light passes through a material. It is defined as the ratio of the speed of light in a vacuum to the speed of light in the material. The RIU is a dimensionless quantity, often expressed as a decimal value. It is a fundamental property of a material that determines how light interacts with it, and is used in various optical applications such as lens design, imaging, and spectroscopy.
