Calculate frequency from period.

To calculate frequency from period, students use f = 1/T after checking that the period is measured in seconds. A period of 0.25 s gives a frequency of 4 Hz because four complete waves pass a point each second. This objective is different from wave-speed calculations because it does not use wavelength. It also protects the boundary between period, which is time for one wave, and frequency, which is number of waves per second. Within the subtopic Properties of waves in Waves in air, fluids and solids, the explanation is anchored to frequency, period and uses those terms in the approved AQA GCSE Physics Waves context.