# Period and frequency

Period is the time for one full cycle. Frequency is cycles per second, in hertz. They are inverses: f = 1/T.

Physics (university) · Part 05: Oscillations and waves · Card 2 of 11 · Last updated 2026-10-19

## Analogy

A heartbeat: 60 beats a minute is 1 Hz.

## Example

**50 Hz mains**

T = 1 / f
T = 1 / 50
T = 0.02 s

## In practice

Mains electricity at 50 Hz repeats every 0.02 s.

## Practice

### Flashcards

- **What is the relation between period and frequency?** f = 1/T.

### Interview questions

**A pendulum clock runs slow on a mountain top. Explain why.**

- Period depends on g
- g is slightly smaller at altitude
- Smaller g gives longer period

## Questions people ask

### What is the difference between frequency and angular frequency?

Frequency f counts cycles per second in hertz. Angular frequency omega counts radians per second, and omega = 2 pi f. One full cycle is 2 pi radians. Equations for oscillations usually use omega, while everyday descriptions of sound and electricity use f.

### How do I find frequency from a graph?

Read the time between two matching points, such as two peaks. That is the period T. Then compute f = 1/T. If peaks are 0.25 s apart, the period is 0.25 s and the frequency is 4 Hz. Count more cycles for better accuracy.

## Related concepts

- [Simple pendulum](https://studyvisually.com/learn/science/physics-university/physics-university-part-5/physics-university-part-5-concept-4)
- [Simple harmonic motion](https://studyvisually.com/learn/science/physics-university/physics-university-part-5/physics-university-part-5-concept-1)
- [Mass on a spring](https://studyvisually.com/learn/science/physics-university/physics-university-part-5/physics-university-part-5-concept-3)
- [Resonance](https://studyvisually.com/learn/science/physics-university/physics-university-part-5/physics-university-part-5-concept-5)

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