What is the definition of frequency?

Frequency is defined as the number of cycles or oscillations that occur in a given time period, specifically measured per second. In the context of wave phenomena, frequency quantifies how many complete cycles of a waveform pass a particular point in one second. This concept is crucial in radiology and physics, as frequency relates to various imaging modalities, including ultrasound and MRI, where different frequencies correspond to different energies and wavelengths of the electromagnetic spectrum.

Option C is correct because it accurately captures this relationship, stating that frequency is about counting the complete cycles of a wave over a standard unit of time (seconds). Understanding frequency helps in analyzing the behavior of waves, including sound waves, light waves, and electromagnetic radiation, which are all integral to radiological practices.