Term information
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency. The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency. Loosely speaking, 1 year is the period of the Earth's orbit around the Sun,[1] and the Earth's rotation on its axis has a frequency of 1 rotation per day.[2] Frequency is also important in the Doppler Effect proposed in 1842 by Christian Doppler. This is used in radar, cooling machines, and predicting weather patterns. unit: For cyclical processes, such as rotation, oscillations, or waves, frequency is defined as a number of cycles per unit time. In physics and engineering disciplines, such as optics, acoustics, and radio, frequency is usually denoted by a Latin letter f or by a Greek letter (nu). In SI units, the unit of frequency is the hertz (Hz), named after the German physicist Heinrich Hertz: 1 Hz means that an event repeats once per second. A previous name for this unit was cycles per second. A traditional unit of measure used with rotating mechanical devices is revolutions per minute, abbreviated RPM. 60 RPM equals one hertz.[3] The period, usually denoted by T, is the length of time taken by one cycle, and is the reciprocal of the frequency f: T = \frac{1}{f} The SI unit for period is the second. source: http://en.wikipedia.org/wiki/Frequency