The amplitude is the height difference between the crest and the trough. The frequency is the number of crests or troughs that pass a given point in a set period of time. The most popular period of time is the second . The number of waves or cycles every second is expressed as a unit called Hertz . The wavelength is the distance travelled in one cycle of a wave.
Radio waves are merely one type of electromagnetic wave.
Conversions Important to always use consistent units. The radio spectrum is split into bands roughly corresponding to the wavelength of the band. From 3 kHz to 30 kHz. Also called very long waves and have wavelengths exceeding 10 000m. From 30 kHz to 300 kHz.