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## 9.4 Period and frequency (ESACV)

Period

The period of a wave is the time taken by the wave to move one wavelength.

Frequency

The frequency of a wave is the number of wavelengths per second.

The period of a longitudinal wave is the time taken by the wave to move one wavelength. As for transverse waves, the symbol T is used to represent period and period is measured in seconds ($$\text{s}$$).

The frequency $$f$$ of a wave is the number of wavelengths per second. Using this definition and the fact that the period is the time taken for $$\text{1}$$ wavelength, we can define:

$f = \frac{1}{T}$

or alternately,

$T = \frac{1}{f}$