Question

the change in a waves direction when it meets a boundary
reflection
resonance
diffraction
refraction

Explanation:

Reflection is defined as the change in a wave's direction when it meets a boundary. Resonance is about the increase in amplitude when a system is driven at its natural frequency. Diffraction is the bending of waves around obstacles or through openings. Refraction is the change in direction of a wave when it passes from one medium to another.

Answer:

Reflection