What is the term for when two or more waves overlap and combine together?

• A. Interference
• B. Reflection
• C. Diffraction
• D. Refraction

Answer: (A)

Interference is what happens when two or more waves overlap and combine. This occurs because waves add their displacements together at every point in space, a idea called the superposition principle. When crests line up with crests, the amplitudes add and you get a larger effect (constructive interference); when a crest meets a trough, they can cancel each other out (destructive interference). This behavior shows up in light, sound, and water waves as patterns of brighter or louder areas and, sometimes, dimmer or quieter areas. The other terms describe different wave behaviors: reflection is the wave bouncing off a surface, refraction is bending as the wave enters a new medium, and diffraction is spreading around edges or through openings. So the term for overlapping and combining waves is interference.