In this video we derive the mathematical expression for the skin depth from Maxwell's equations, and calculate the skin depth for a few materials of interest to the radio experimenter. Similar treatments can be found in published notes, including http://www2.ph.ed.ac.uk/~mevans/em/lec19.pdf and https://ecee.colorado.edu/~ecen4634/Chapter%2020%20-%20The%20Skin%20Effect.pdf, as well as books on the physics of electricity and magnetism.