# Dictionary:Skin depth

The effective depth of penetration of electromagnetic energy in a conducting medium when displacement currents can be neglected. The depth at which the amplitude of a plane wave has been attenuated to 1/e (or 37 percent):

where =conductivity in mhos/meter, =permeability in henries/meter, =angular frequency in radians/second, and *f*=frequency. Also called **effective depth**.