What physical quantity is measured in Hertz (Hz)?

Hertz (Hz) is the unit of frequency in the International System of Units (SI). It measures the number of cycles of a periodic phenomenon that occur in one second. For example, in the context of sound waves, if a sound wave has a frequency of 440 Hz, it means that 440 cycles of the wave occur each second, which corresponds to the pitch of the note A above middle C.

Understanding frequency as a measure of how often an event occurs over time is fundamental in various scientific fields such as physics, engineering, and communication. In contrast, options like wavelength and amplitude refer to different characteristics of waves. Wavelength measures the distance between successive crests of a wave, while amplitude refers to the height of the wave and is related to the energy or intensity of the wave. Capacitance, on the other hand, is a measure of a capacitor's ability to store electrical charge and is unrelated to wave properties. Thus, the correct answer highlights the specific measurement of the cyclical behavior of waves, which is frequency.