When an amplitude-modulated (AM) wave is transmitted through air or any other medium, it does not change the frequency of the carrier signal. The carrier signal's frequency remains constant throughout the transmission.
In AM modulation, the information is encoded in the amplitude variations of the carrier wave. The carrier wave has a fixed frequency, typically in the radio frequency range. The modulating signal, which carries the information to be transmitted, is superimposed onto the carrier wave by varying its amplitude.
During transmission through air, the AM wave propagates as an electromagnetic wave. Electromagnetic waves consist of an electric field and a magnetic field oscillating perpendicular to each other and to the direction of wave propagation. The frequency of the carrier wave determines the number of oscillations of the electric and magnetic fields per second.
As the AM wave travels through the air, it experiences various phenomena such as diffraction, reflection, and refraction. These phenomena affect the propagation characteristics of the wave, but they do not alter the frequency of the carrier signal.
The demodulation process, which takes place at the receiver, separates the original modulating signal from the AM wave by extracting the variations in amplitude. The carrier frequency is used as a reference to recover the modulating signal, allowing the original information to be reconstructed.
In summary, the frequency of an AM wave, including the carrier signal, remains unchanged when it passes through the air or any other transmission medium. The modulation scheme only affects the amplitude of the carrier wave, allowing the encoded information to be transmitted and subsequently demodulated.