What is the unit of frequency?

The unit of frequency is Hertz (Hz). Frequency measures how many cycles of a periodic event occur in one second. The term Hertz is defined as one cycle per second, making it the appropriate unit to quantify frequency in various contexts, such as electrical signals or sound waves.

In understanding why Hertz is the correct answer, it's essential to recognize the specific roles of the other units mentioned. Watt (W) is a unit of power, which quantifies the rate of energy transfer. Ohm (Ω) is the unit of resistance, indicating how much a material opposes the flow of electric current. Joule (J) is a unit of energy or work done. Each of these units pertains to different aspects of electrical and physical phenomena, but none serve to measure frequency. Thus, Hertz stands out as the correct answer, directly relating to the measurement of how frequently an event occurs per unit time.