When an electromagnetic (EM) wave enters a conducting medium, such as a metal, several things happen:
Reflection: The incident wave partially reflects off the surface of the conductor, similar to the reflection of light off a mirror. This reflection occurs because the conducting medium cannot support the propagation of the EM wave as effectively as a non-conducting medium.
Absorption: A portion of the incident wave is absorbed by the conducting medium. The conducting material converts the energy of the EM wave into heat due to the resistance it offers to the flow of electric current. This absorption results in a decrease in the intensity of the wave as it propagates through the conductor.
Transmission: In some cases, a small fraction of the EM wave can penetrate the conducting medium and propagate through it, especially at high frequencies. However, the extent of transmission depends on the conductivity and thickness of the material. As the conductivity of the medium increases, the transmission of the EM wave decreases.
Skin Effect: For high-frequency EM waves, there is a phenomenon called the "skin effect." This effect causes the EM wave to be concentrated near the surface of the conducting medium. The higher the frequency, the shallower the depth of penetration into the conductor. This behavior is due to the interaction between the EM wave and the induced electric currents within the conductor.
In summary, when an EM wave enters a conducting medium, it experiences reflection, absorption, and possible transmission, with the amount of each depending on factors like the conductivity and frequency of the wave.