What is the phenomenon called when two waves combine to produce a smaller amplitude wave?

When two waves combine to produce a smaller amplitude wave, this phenomenon is known as destructive interference. This occurs when the peaks (crests) of one wave align with the troughs of another wave, effectively canceling each other out to some extent. As a result, the combined wave has a lower amplitude than either of the individual waves.

Destructive interference is significant in various contexts, such as sound waves, light waves, and water waves, where it can lead to effects like noise cancellation or the phenomenon of reduced brightness in certain areas when light waves overlap destructively.

Constructive interference, on the other hand, refers to the scenario where waves align in such a way that their amplitudes reinforce each other, leading to a larger combined amplitude. Reinforcement is not formally recognized in wave theory as a distinct phenomenon. Reflection pertains to the bouncing back of waves when they encounter a barrier, which is unrelated to amplitude changes.