Final answer:
Reflection is the change in direction of a wave when it bounces off a barrier, such as when sound waves reflect off a surface and create echoes.
Step-by-step explanation:
The term reflection refers to the change in direction of a wave when it bounces off a barrier. This behavior occurs when waves, such as sound waves, collide with an object and the individual particles that are oscillating within the wave bounce off, causing the entire wave to reflect. This scenario is evident when we hear echoes as sound waves reflect off a rigid surface. The reflection of a wave is particularly evident at the boundary of a medium, where the incident wave encounters a boundary and becomes a reflected wave. A fixed boundary will reflect the wave with an inversion, whereas a free boundary will not cause an inversion.