Why does diffuse scattering occur?

Diffuse scattering occurs when light interacts with a rough surface that has various orientations. When light strikes such a surface, it can scatter in many directions rather than reflecting uniformly. This scattering happens because the microscopic irregularities in the rough surface cause the light rays to bounce off at different angles, leading to a diffuse, non-uniform reflection.

In contrast, when light meets a polished surface, it reflects in a more organized manner, resulting in specular reflection rather than diffuse scattering. Likewise, light traveling through a vacuum does not encounter any surface to scatter off of, nor does complete absorption by a material contribute to scattering; instead, it simply removes the light from the system. Therefore, the rough surface with different orientations is the key factor that leads to diffuse scattering, making it the correct answer.