Which property of waves is used to describe how they may bounce off surfaces and change direction?

The property of waves that describes how they may bounce off surfaces and change direction is reflection. When a wave encounters a surface or an obstacle, some or all of its energy can be reflected back into the original medium. This behavior is significant in various applications, such as in the functioning of mirrors and in acoustics.

Reflection occurs when the wave front hits a boundary; depending on the nature of that boundary, the angle at which the wave hits the surface (the angle of incidence) will equal the angle at which it reflects away (the angle of reflection). This principle is crucial for understanding not only light waves but also sound waves and waves on water.

The other properties mentioned—refraction, diffraction, and absorption—relate to different behaviors of waves. Refraction describes the bending of waves as they pass from one medium to another at an angle, diffraction refers to the spreading of waves when they pass through a narrow opening or around obstacles, and absorption involves the energy of the wave being taken in by the medium rather than being reflected. Therefore, reflection specifically pertains to the bouncing behavior and change in direction of waves.