Interface

A wave carries energy towards an interface: the boundary between two materials. At the boundary, some of the wave may be reflected back, some may be transmitted into the second material, and some may be absorbed. These are not always either-or outcomes.

When it reaches an interface—the boundary between two materials—several things may happen. Some of the wave may be reflected back into the material it came from, some may be transmitted into the second material, and some may be absorbed, transferring energy to the material. These are not necessarily alternatives: all three can occur at the same interface.

When it reaches an interface—the boundary between two materials—it may be reflected back or pass into the new material. Ripples reaching the side of a tank make reflection easy to see; water waves can also model how light and sound behave at boundaries.