21. A measure of the depth to which radiation can penetrate the shield is the so-called skin depth . 22. At low frequencies, the SPP penetration depth into the metal is commonly approximated using the skin depth formula. 23. Where the thickness is less than the skin depth , the actual thickness can be used to calculate surface resistance. 24. So earths magnetic field will make its way through . ( A super conductor will have 0 skin depth ). 25. The appropriate skin depth is not just the depth at the fundamental, but also the skin depths at the harmonics. 26. The appropriate skin depth is not just the depth at the fundamental, but also the skin depths at the harmonics. 27. :The skin depth for a 1 GHz signal in seawater is roughly 1 centimeter ( about half an inch ). 28. This reduces the skin depth for iron to about 1 / 38 that of copper, about 220 micrometres at 60 Hz. 29. The skin depth is the distance which the wave can travel before its " amplitude " reduces by that same factor. 30. At 500 kHz, the skin depth in copper is about a dimension smaller than the typical wires used in a power supply.
