What is the phenomenon where light bounces off a surface called?

The phenomenon where light bounces off a surface is called reflection. Reflection changes the direction of light at an interface, sending it back into the medium from which it came. It is why mirrors produce images and why objects are visible when light reaches our eyes from their surfaces.

On a smooth surface, light undergoes specular, or regular, reflection. The angle at which the light strikes the surface equals the angle at which it leaves, with both angles measured from the normal—a line perpendicular to the surface. Rough surfaces produce diffuse reflection, scattering light in many directions. Most everyday objects are seen primarily through diffuse reflection rather than mirror-like reflection.

Reflection differs from refraction, which is the bending of light as it enters a different medium. Absorption occurs when a material takes in light energy, often converting it to heat. Diffraction is the spreading or bending of waves around edges and through openings. Reflection is not limited to visible light: radio waves, sound waves, water waves, and seismic waves can all reflect.