In the International System of Units, what is the standard SI unit used to measure frequency, that is, the number of oscillations or cycles per second?

Introduction / Context:
Frequency is a fundamental concept in physics and engineering. It describes how many cycles, oscillations, or repetitions of a periodic event occur in one second. This is important in the study of sound waves, electromagnetic waves, alternating current circuits, and many other systems. The question asks you to identify the correct SI unit of frequency from a list of common units used for other physical quantities.

Given Data / Assumptions:
- Frequency is defined as number of cycles per second.- We are working within the International System of Units.- The options include units that belong to different domains of physics.

Concept / Approach:
In the SI system, the unit of frequency is the hertz, symbol Hz. One hertz corresponds to one cycle per second. Other units listed in the options relate to force, power, and capacitance: newton for force, watt for power, and farad for capacitance. Only hertz has the correct dimensional interpretation as reciprocal seconds, which aligns with the definition of frequency. Remembering this association is important for understanding wave equations and alternating current descriptions.

Step-by-Step Solution:
1. Start from the definition: frequency f is equal to the number of cycles N divided by time t.2. The unit of N is dimensionless count, and the unit of time t is second, so the unit of f is 1 per second.3. In SI, one cycle per second is given a special name, hertz, abbreviated as Hz.4. Check the options: newton is unit of force, watt is unit of power, farad is unit of capacitance, and hertz is the only one that matches reciprocal seconds.5. Therefore, hertz is the correct SI unit for frequency.

Verification / Alternative check:
Look at common devices and descriptions: tuning radios to a certain frequency in megahertz, power systems operating at 50 Hz or 60 Hz, and audio tones described as, for example, 440 Hz for concert A. In all such real world examples, frequency is always expressed in hertz or multiples like kilohertz or megahertz. This widespread usage confirms that hertz is the correct SI unit of frequency.

Why Other Options Are Wrong:
- Newton: It is the SI unit of force, associated with mass times acceleration.- Watt: It is the SI unit of power, equal to one joule per second.- Farad: It is the SI unit of capacitance in electric circuits.

Common Pitfalls:
Because many units appear across different branches of physics, students may confuse them if they are not careful about the context. Remembering typical uses can help: newton for weight and forces, watt for electrical and mechanical power, farad for capacitors, and hertz for waves and oscillations. Keeping a mental map of which unit belongs where will make such questions easy to answer.

Final Answer:
The SI unit of frequency is hertz, corresponding to one cycle per second.