What is the SI unit of frequency?

The SI unit of frequency is Hertz. Frequency measures how often an event occurs in a given timeframe, typically measured in cycles per second. One hertz is defined as one cycle per second, making it an essential unit in various fields, including physics, electronics, and wave mechanics.

The other options represent different physical quantities: Joule is the unit of energy, Newton is the unit of force, and Pascal is the unit of pressure. Each of these units serves distinct purposes and relates to different aspects of physics, which highlights the specificity of the term "frequency" and its appropriate unit, Hertz.