Refraction is the name of that change of direction. When light (and sometimes sound, or a radio wave) moves from one material into another — air to water, air to glass — it changes speed, and so it changes path. That event is refraction. Physics, glasses, and photography need the noun because they talk about the amount of bend, not only the verb “it bends.” Though actually, the line you often see, “glass refracts light,” is the action; refraction is the happening, or the result. A pool can look shallower than it is because of refraction, and a lens works because of it. Keep it apart from reflection, which is bouncing back from a surface.