Refractometry is a technique used to measure the refractive index of a substance, which indicates how light propagates through it. This property is crucial in various fields, including chemistry, biology, and material science, as it helps identify and characterize different materials based on their optical properties. The process involves passing light through a sample and measuring the angle of refraction. By comparing this angle to that of a reference, scientists can determine the refractive index. This method is widely used in quality control, food industry, and pharmaceuticals to ensure product consistency and purity.