The phenomenon that causes light to bend is known as refraction. Refraction occurs when light travels from one medium to another with a different density, such as from air into water or glass. As light passes through different materials, its speed changes, resulting in a change in direction. This bending of light is what causes objects to appear distorted when viewed through a glass of water. Refraction is also the principle behind lenses in glasses, cameras, and microscopes, allowing these devices to focus light and magnify images effectively.