Which phenomenon describes the height of a wave's peak?

The phenomenon that describes the height of a wave's peak is the amplitude. Amplitude refers to the maximum displacement of points on a wave from their rest position, indicating how high or low the peaks and troughs of the wave are in relation to a baseline. This measurement is crucial in various fields, including optics and acoustics, as it directly relates to the energy carried by the wave; higher amplitudes usually correspond to greater energy levels.

In a wave context, frequency pertains to how often the wave cycles occur in a given time period, while wavelength is the distance between successive peaks or troughs. Velocity refers to the speed at which the wave travels through a medium. Therefore, none of these concepts accurately capture the notion of the 'height of a wave's peak' as effectively as amplitude does.