Which term describes the number of cycles or wavelengths per second for waves?

The concept of frequency directly relates to the number of cycles or wavelengths that occur in a given time frame, specifically one second. Frequency is measured in hertz (Hz), with one hertz equating to one cycle per second. This measurement is crucial for understanding various wave phenomena, including sound and electromagnetic waves.

When discussing waves, frequency informs us how often the wave oscillates or vibrates, which is a key feature influencing properties such as pitch in sound waves. For instance, a higher frequency means more wave cycles happen in one second, resulting in a higher pitch sound.

In contrast, amplitude refers to the height of the wave and is a measure of the wave's energy but does not indicate how frequently the cycles occur. Velocity deals with the speed at which the wave travels through a medium but does not specify the number of cycles per second. Pitch, while related to sound frequency, specifically describes the perception of how high or low a sound is based on its frequency rather than the measurement itself. Hence, the term that correctly describes the number of cycles or wavelengths per second is frequency.