The phenomenon that describes the bending of a wave as it passes from one medium to another is refraction. This occurs due to a change in the speed of the wave as it enters a new medium, which results in a change in direction. For example, when light travels from air into water, it slows down, causing it to bend at the interface between the two mediums. This bending effect is responsible for many practical occurrences, such as the way a straw appears bent when placed in a glass of water.
In contrast, diffraction refers to the spreading out of waves when they encounter an obstacle or pass through a narrow opening, while reflection involves the bouncing back of waves when they hit a surface. Dissipation generally refers to the gradual loss of energy in a system, such as when a wave loses its intensity due to spreading out or absorption, rather than bending. Understanding refraction is essential in various fields, including optics and acoustics, as it helps explain how waves behave under different conditions.