KinexiaLEARN PHYSICS

Wave Period — Ocean Swell Frequency (Worked Example)

Easy
Problem

Ocean swells roll onto a beach once every 8.0 seconds. What is the frequency of the swell?

Given

  • T = 8.0 s

Find

The frequency f.

Principle

Frequency is the reciprocal of period: f = 1/T — how many waves pass per second.

Formula

Solution

  1. Write the formula: f=1/Tf = 1/T

  2. Substitute: f=1/8.0f = 1/8.0

  3. Calculate: f=0.125 Hzf = 0.125\ \mathrm{Hz}

0.125 Hz

Unit check

1 ÷ s = Hz — correct.

What this means physically

0.125 Hz — one wave every 8 seconds. Long-period swells like this travelled thousands of kilometres from a distant storm; short chop has periods under 3 s.

Common mistake

Writing 8 Hz. The period (8 s) is the time per wave; frequency is waves per time — the reciprocal.