Wave period
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The period of a wave is the time the full wave takes to pass a given point. The period, T and the frequency f obey the following relation,
- <math>T=\frac{1}{f}<math>,
where f is the frequency of the wave, measured in inverse seconds (s-1 or hertz (Hz)) and T is the period, measured in seconds.
Since
- <math>v = f \lambda \,<math>,
where v is the wave speed, measured in metres/second (m/s) and λ is the wavelength, measured in metres (m), we have the following relation for T:
- <math>T = \frac{\lambda}{v}<math>
Usage of period versus frequency
As a matter of convenience, longer and slower waves, such as ocean surface waves, tend to be described by period rather than frequency. Short and fast waves, like audio and radio, are usually described by their frequency or wavelength instead of period. These commonly used conversions are listed below:
| Frequency: | 1 mHz (10-3) | 1 Hz (100) | 1 kHz (103) | 1 MHz (106) | 1 GHz (109) | 1 THz (1012) |
| Period (time): | 1 ks (103) | 1 s (100) | 1 ms (10-3) | 1 µs (10-6) | 1 ns (10-9) | 1 ps (10-12) |