Which kinds of surfaces are the most reflective?

The term “reflect” means "to bounce off of." Both light and sound waves can reflect off of surfaces.

Hard, shiny surfaces are the best kind of surfaces for the reflection of light. Light tends to bounce off of such surfaces at the same angle at which the light hits the object. Examples of such smooth and shiny materials are mirrors, glass, still water, and metals. Rough but shiny surfaces tend to reflect light in all directions. In other words, rough, shiny surfaces scatter the light. Rough and opaque surfaces are poor reflectors of light.

An echo is a reflected sound. Hard and smooth surfaces are the best kind of surfaces to reflect sound. This is why your voice echoes so well in a gymnasium that has smooth wood floors and cement walls. On the other hand, sound does not reflect (echo) well on rough and soft surfaces. This is why you voice does not echo well in a carpeted room.