AC foundations
Wavelength
- where
- wavelength (m)
- wave speed in medium (m/s)
- frequency (Hz)
Explain this equation
Works out the wavelength of a signal from its speed and frequency. Useful for aerials and cable lengths.
λ is the wavelength in metres: the length of one full cycle. v is the wave speed in the medium. f is the frequency in hertz.
In one cycle the wave travels v ÷ f metres, so that is its wavelength. Higher frequency means shorter waves at the same speed.
Sense check: 100 MHz at 300,000,000 m/s is 3 m. At 50 Hz, the mains wavelength is about 6,000 km.
Watch out: signals travel slower in cable than in free space, so use the speed for the medium. And 1 MHz is 1,000,000 Hz.
At a fixed propagation speed, higher frequency gives shorter wavelength. Divide the supplied speed by frequency.
Use hertz rather than megahertz unless you make the corresponding conversion.
Enter your values to see the result.
Common mistake
Forgetting that 1 MHz = 1,000,000 Hz.
Limits
Use the speed for the stated medium, not automatically vacuum speed.
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.