AM Radio waves   Radio waves are electromagnetic radiation propagating though the air like a sine wave on a sine wave.  Medium waves are most commonly known as AM  radio and broadcast at 520-1610 kHz in the Americas.  Electromagnetic radiation is created by an alternating current in a wire or conductor, creating an electromagnetic field and the radiation energy travels at the speed of light. Amplitude Modulated:  the change in signal is carried on the amplitude or wave height, the sound is added to the sine wave thus changing the wave height or amplitude.         Velocity = (frequency) (wave length)  AM wavelength is constant because the frequency is constant and the electromagnetic waves create resonance currents on antennas (conductors) of length equal to the wave length or some harmonic multiple of the wave length.  AMPLITUDE:  "The maximum displacement form equilibrium of an element of the medium is called the amplitude A of the wave." (Serway p 492) FREQUENCY:  "In general,  the frequency of a periodic wave is the number of crests (or troughs, or any other point on the wave) that pass a given point in a unit time interval... f=1/T"  this is commonly in the units of hertz which is one over seconds.  (Serway p 492) WAVE LENGTH:  "The distance form one crest to the next is called the wavelength λ (greek lambda)..." (Serway p 492)