How is the amplitude of a wave defined?

The amplitude of a wave is defined as the height from the resting point (equilibrium position) to the crest (the highest point of the wave). This measurement indicates the maximum displacement of points on a wave from their rest position, which is essential for understanding the wave's energy and intensity. A larger amplitude means that the wave carries more energy, resulting in a louder sound in the case of sound waves or a brighter light in the case of electromagnetic waves.

The other options do not accurately represent the definition of amplitude. The distance between waves refers to wavelength, while total energy pertains to the wave's energy content, and the speed of wave propagation describes how fast the wave travels through a medium. In this context, option B is the most directly aligned with the definition of amplitude.