What is the complementary unit for Hertz (Hz)?

The complementary unit for Hertz (Hz) is the Pulse Repetition Period (PRP). Hertz measures frequency, which is defined as the number of cycles per second. In sonography and other applications, the frequency of a pulse emitted by a transducer can be inversely related to the time between each pulse being emitted, which is described by the PRP.

When you know the frequency of the ultrasound pulse (in Hertz), the PRP can be calculated using the formula:

[ PRP = \frac{1}{\text{Frequency}} ]

This means that a higher frequency corresponds to a shorter PRP, while a lower frequency corresponds to a longer PRP. Thus, they are complementary in that they represent different aspects of the same phenomenon: the elapsed time for a sequence of events (in PRP) versus the rate at which these events occur (in Hertz).

Other choices represent different concepts not directly complementary to Hertz. Milliseconds is a unit of time but does not denote frequency directly. Kilohertz is simply another unit of frequency and is not complementary. The Duty Factor relates to the fraction of time that ultrasound is being transmitted versus the total time of the pulse cycle, which does not have a direct inverse relationship with Hertz.