electromagnetic penetration depth

The term "electromagnetic penetration depth" is closely related to the "skin effect" in physics. The skin effect describes how alternating, high-frequency electric currents tend to concentrate near the surface of a conductor. This phenomenon increases the conductor's resistance because the current is confined to a smaller cross-sectional area.1

The depth to which electromagnetic waves can penetrate a conducting material is also dependent on the frequency of the radiation and the conductivity of the medium. This depth is known as the skin depth, denoted by the Greek letter delta ((\delta)). It represents the distance within the conducting medium where the amplitude of the electromagnetic wave decreases to approximately 1/e (about 37%) of its initial value. At high frequencies, the skin depth is small, meaning the waves do not penetrate deeply into the conductor.2