Waves and boundaries• A boundary is a place where conditions change.

What a wave does at a boundary depends on the boundary conditions.

The wave approaching a boundary is called the incident wave.

The wave returning from a boundary is called the reflected wave.

Refraction of waves involves a change in the direction of waves as they pass from one medium to another.

Diffraction - a change in direction of waves as they pass through an opening or around a barrier in their path