What defines constructive interference?

Constructive interference occurs when two waves interact in such a way that their crests and troughs align, resulting in a larger amplitude wave. This happens when the waves are in phase, meaning the peaks (crests) and valleys (troughs) of each wave coincide perfectly. When this alignment occurs, the combined wave has greater energy and intensity than either of the individual waves alone. This phenomenon is fundamental in various applications, such as sound engineering and optical systems, where enhancing signals is essential.

The other choices refer to different types of wave interactions that do not describe constructive interference. For example, waves meeting out of phase leads to destructive interference, where the combined wave has a reduced amplitude. Similarly, waves causing cancellation or reducing overall energy also pertain to destructive interference. Therefore, the statement about waves amplifying each other when in phase accurately defines constructive interference and illustrates its role in wave phenomena.