What is defined as the amplitude of a wave?

The amplitude of a wave is defined as the maximum height of the wave from its undisturbed position (or equilibrium position) to the crest. This measurement is a crucial characteristic of waves, as it reflects the energy carried by the wave; a larger amplitude indicates that the wave carries more energy.

The amplitude is typically observed in both transverse waves, where the motion of the wave is perpendicular to the direction of energy transfer, and in longitudinal waves, where the motion is parallel. Understanding amplitude is important in various fields, such as sound and light waves, as it influences how we perceive volume or brightness.

The other options describe different aspects of waves: the distance from the trough to the crest relates to the wave's height but does not specify the amplitude definition correctly, as it includes more than just the amplitude alone. The distance traveled by a wave is related to its wavelength and speed, while frequency refers to how many waves pass a point in a given time, neither of which defines amplitude.