The rate of repetition of periodic motion measured in hertz (cycles per second). Rate of repetition of changes.


f = frequency [Hz]
T = period [s]
v = wave speed [ms-1]
λ = wavelength [m]
ω = angular frequency [rad s-1]

Enter values into 2 of the 5 fields. The others will be calculated.

For low frequency events (e.g. long pendulum) the frequency can be measured by counting the number of complete cycles and dividing by the total time for those cycles.

infrasound<20 Hz
lower audible limit20 Hz
middle C264 Hz
treble A440 Hz
upper audible limit20000 Hz
VHF radio30 to 300 MHz
UHF radio300 to 3000 MHz
Red end of visible spectrum4.284x1014Hz
Violet end of visible spectrum7.495x1014Hz


This is an abbreviation for the latin phrase bis in die which translates to "twice a day". This is a unit of frequency traditionally used when prescribing medicine.

diebus alternis

Latin for every other day. Unit of frequency used in prescribing medicine.

diebus tertius

Latin for every third day. Unit of frequency used in prescribing medicine.

in die

Latin meaning daily. Unit of frequency used in medical prescriptions.

See also: Angular Frequency, Audio Frequency, Bandwidth, Doppler Effect, Extremely High Frequency, Extremely Low Frequency, Frequency Spectrum, Fundamental, Group Delay, Harmonic, Hertz, High Frequency, Low Frequency, Medium Frequency, Octave, Per Diem, Per Mensem, Period, Phase, Ultra Low Frequency, Very High Frequency, Wavelength.

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Subjects: Physics

NASA Electromagnetic Spectrum Page A NASA page on the electromagnetic spectrum.