Frequency
Frequency measures repeating events per unit time.
Frequency is the number of occurrences of a repeating event per unit of time. It is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals, radio waves, and light. The interval of time between events is called the period, which is the reciprocal of the frequency.
- definition
- Number of cycles or repetitions per unit time
- symbol
- f or ν (Greek letter nu)
- SI unit
- hertz (Hz)
- related_quantity
- Period T = 1/f
- other_units
- revolution per minute (rpm), radian per second (rad/s)
Lore & Background
Frequency is defined for cyclical phenomena such as oscillations, waves, or simple harmonic motion. The conventional symbol is f or ν. The period T is the time taken to complete one cycle, and the relationship is f = 1/T. Temporal frequency emphasizes occurrences per unit time. A traditional unit for rotating devices is revolution per minute (rpm), where 60 rpm equals one hertz.
Reader's Guide
Frequency is a fundamental parameter across science and engineering, describing how often a repeating event occurs per unit time. Its reciprocal, the period, is used for longer and slower waves like ocean surface waves, while frequency is preferred for short and fast waves such as audio and radio. Related quantities include rotational frequency (rate of change of number of rotations) and angular frequency (rate of change of angular displacement, ω = 2πf). Spatial frequency applies to properties varying in geometry. For periodic waves, frequency relates to wavelength and phase velocity: f = v/λ. Measurement methods include counting events over a time interval, which introduces gating error, and using a stroboscope for rotating or vibrating objects. The hertz, as the SI unit, standardizes frequency measurement globally.
Did You Know?
- Sixty rpm is equivalent to one hertz.
- Angular frequency is frequency multiplied by 2π.
- For electromagnetic waves in vacuum, frequency equals the speed of light divided by wavelength.
More in Electromagnetism And Waves 1-23
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