Frequency is a measurement of how often a recurring event such as a wave occurs in a measured amount of time. One completion of the repeating pattern is called a cycle. Only moving waves which vary their positions with respect to time possess frequency. Frequency is one way to define how fast a wave moves.
Waves can move in two ways. The frequencies of progressive waves or those that move forward indicate how fast a wave moves forward in units of cycles per unit time. The frequencies of standing waves or those that oscillate in place are the rate of oscillation in units of cycles per unit time.
The dictionary definition of frequency is:
Physics. a) the number of periods or regularly occurring events of any given kind in a unit of time, usually one second.
b) the number of cycles or completed alternations per unit time of a wave or oscillation.
Symbol: f; Abbr.: freq.
Frequency is expressed in units of cycles per unit time.
Although frequency is a measurement of rate of movement, it is not identical to velocity. For example, if we think of a car that moves at 60 miles per hour, we mean just that. However, if we say that a wave has a frequency of 60 cycles per hour, points on the wave may be traveling faster or slower depending on wavelength. Comparing two waves of the same wavelength, a higher frequency is associated with faster movement. Comparing two waves of different wavelengths, a higher frequency doesn't always indicate faster movement, although it can. Waves of different wavelengths can have the same frequency. For some purposes, the measurement frequency is more useful than absolute velocity.
The unit, Hertz
The unit Hertz (Hz) is used to describe frequency in cycles per second. In a sentence the proper format for writing this relationship is:
One cycle represents the movement of one wavelength.
Radio call numbers
Often you might hear radio frequencies given in Megahertz (MHz) ... (under construction).
Wave frequency is also related to another measurement called the wave period (T). The wave period is just how much time it takes for one cycle to pass and the units are always in terms of time. The faster a wave moves, its wave period becomes smaller.
Instead of measuring in terms of a fixed time unit, the second, the wave period uses a fixed number of cycles, one cycle ...
How do you measure wave period?
Wave period can be determined by measuring how much time it takes two peaks to pass a certain point. You can do this for ocean waves by standing on a pier and using a stop watch.