AC foundations
Wave speed
- where
- wave speed (m/s)
- frequency (Hz)
- wavelength (m)
Explain this equation
Works out how fast a wave travels from its frequency and wavelength. Used in signal and radio work.
v is the wave speed in metres per second. f is the frequency: cycles per second. λ (lambda) is the wavelength: the distance of one full cycle.
Each second, f cycles pass, and each cycle is λ long, so the wave covers f × λ metres per second.
Sense check: 100 Hz with a 3 m wavelength gives 300 m/s. Radio waves in air travel at about 300,000,000 m/s.
Watch out: this is the speed of the signal, not of the electrons, which drift very slowly.
A wave travels one wavelength in one period. Multiplying cycles per second by metres per cycle gives metres per second.
Wave propagation and electron drift are different motions. Use this relationship for the specified wave and medium.
Enter your values to see the result.
Common mistake
Treating signal speed as the speed of individual electrons.
Limits
Wave speed depends on medium; not an electron-drift formula.
Sources
The tools calculate the displayed equation. They do not automatically choose cable sizes, approve installations, supply current regulatory tables, certify equipment or replace inspection and testing.