Consider a ball floating on the surface of a water wave. The ball moves up and down in a simple harmonic motion. The highest point of the wave is known as the crest, and the lowest point is known as the trough. The distance between two consecutive troughs or crests with the same height and the same slope is the wavelength of a wave. The amplitude of the wave is the maximum height measured from the equilibrium position and is directly related to the amount of energy carried by the wave. The time taken for one complete oscillation of the ball is the wave's period T. Consider that the ball is at a fixed position. Then, the number of waves that pass the ball in a unit of time is the wave's frequency. The speed of a wave is defined as the distance traveled in a given amount of time. Wavelength is the distance traveled by the wave in one wave period. Hence, wave speed equals wavelength times frequency.