What term describes the number of wave crests that pass a fixed point during a particular period of time?

Frequency is the term that specifically refers to the number of wave crests that pass a fixed point during a given period of time. In the context of waves, frequency is measured in hertz (Hz), which indicates how many cycles (or crests) occur in one second. This concept is crucial in fields such as physics and telecommunications, where understanding wave behavior is essential for analyzing signals and communication systems.

Amplitude refers to the height of the wave crest from its rest position and is related to the wave's energy, not the number of crests that pass a point. Wavelength is the distance between successive crests of a wave, which describes the spatial characteristics of the wave rather than the rate at which crests pass a point. Velocity, in the context of waves, refers to how fast the wave propagates through space, which is influenced by both frequency and wavelength but does not specifically indicate how many crests pass by in a given time frame. Thus, frequency is the most appropriate term that directly answers the question about the number of wave crests passing a fixed point over time.