Frequency
The frequency of a wave can be described using two definitions:

Frequency, f, is proportional to the reciprocal of the wavelength, λ, and is related to the speed of light(c) in a vacuum. This means that longer wavelengths correspond to lower frequency and shorter wavelengths correspond to a higher frequency, according to the following equation:

Frequency is also defined as the number of complete cycles occurring per period, T, of time. The SI unit of frequency is Hertz, defined as 1 Hz = 1 s^{1}. The shorter the period, the larger the frequency.
The following equation defines frequency as the reciprocal of the period of the oscillation, T: