Which wave phenomenon occurs when two waves meet to produce a larger amplitude?

• A. Refraction
• B. Diffraction
• C. Destructive interference
• D. Constructive interference

Answer: (D)

When two waves overlap, their displacements add at each point — the superposition principle. If they line up so that peaks meet peaks and troughs meet troughs, their amplitudes reinforce each other, giving a larger overall amplitude. This is called constructive interference.

Other phenomena involve different behavior: refraction is bending due to a change in speed in a new medium, and diffraction is the spreading or bending of waves around obstacles or through openings. Destructive interference is the opposite situation, where overlapping waves are out of phase and cancel each other, reducing amplitude. Thus, producing a larger amplitude when they meet is exactly constructive interference.