The phenomenon of light bending as it passes through different mediums is called refraction. Refraction occurs when light travels through substances with varying densities, causing its speed and direction to change. This principle is fundamental in optics and is responsible for various effects, such as the bending of a straw appearing submerged in water or the focusing of light through lenses in glasses and cameras. Understanding refraction is essential for applications in vision correction, photography, and scientific instruments.