### Frequency

Angular frequency is a cycle of repetition and refers to the angles covered by a frequency. Thus angular frequency is equal to:

A bicycle wheel turning at the rate of five cycles per second will
scan an angle of *10π* radians per
second. Angular frequency is in units of radians per
second.

When a cycle completes, it does so in a given period of time. The period of time to complete a cycle is the reciprocal of the frequency:

A bicycle wheel turning at five cycles per second will have a period of 1/5 second. Or in other words, the time it takes to turn the wheel once at five cycles per second will be 1/5 second.

Not all cycles are stationary and go in circles. Quite often a cycle is associated with a velocity. As a bicycle wheel turns and completes one cycle, the rider of the bike will travel a distance. This distance is called the "wavelength" when applied to photons. The distance the bicycle rider will travel will depend on its velocity per frequency:

So if the rider travels five feet per second, and the wheel turns at five cycles per second, then the rider has traveled one foot (the bicycle would be very small!).