The phenomenon that causes light to bend when it passes through different mediums is known as refraction. Refraction occurs because light travels at varying speeds in different materials, causing it to change direction at the interface between two media. This bending of light is responsible for numerous optical phenomena, such as the apparent distortion of objects submerged in water or the dispersion of light through a prism. Understanding refraction is crucial in optics, affecting the design of lenses, glasses, and various optical instruments.