Given the task definition and input, reply with output. Given a scientific passage and an answer, generate a question for the given answer.

Passage: The angle of reflection equals the angle of incidence. A mirror has a smooth surface and reflects light at specific angles. Light is diffused when it reflects from a rough surface. Mirror images can be photographed and videotaped by instruments. Answer: rough surfaces
What kind of surface would cause diffusion when light is reflected off of it?