Frequency is measured in

Analyze the question: You are asked for the unit used to measure frequency.

Explain the concept: Frequency is the number of complete cycles (or oscillations or waves) that occur in one second.

Formula: f = 1/T, where T is the period in seconds.

Since T is in seconds, f has units of 1/seconds (s⁻¹). This unit is given a special name, the hertz (Hz), in honour of Heinrich Hertz.

Check each option:

• A. meter per second is the unit of speed or velocity, not frequency.
• B. seconds is the unit of time and of the period (T). Frequency is its reciprocal, so it is not measured in seconds.
• C. hertz is correct. 1 Hz = 1 cycle per second = 1 s⁻¹.
• D. farad is the unit of capacitance, not frequency.

Answer: The correct option is C. hertz.

Tip: Remember the pair "Period in seconds, frequency in hertz." They are reciprocals: f = 1/T. For example, a radio station at 100 MHz means 100 million cycles every second. Also remember wave speed v = fλ, which gives m/s = Hz × m, so speed is the "meter per second" in option A, not frequency.