In order to transmit information via radio waves, the waves need to be changed somehow. For car radios this can happen in two ways. For AM radios, which property of the carrier wave is modulated before it is transmitted?

Answer: amplitude

Explanation: This describes the maximum amount of the displacement of a particle from it rest position. Usually, it is measured in metres

Since we are considering AM which is amplitude modulation, a technique used in electronic communication, most commonly for broadcasting information through a radio carrier wave. In amplitude modulation, the amplitude (signal strength) of the carrier wave is diversified in proportion to that of the message signal being broadcasted.