Penetration depth refers to the distance into a superconductor that an external magnetic field can effectively penetrate before being expelled. This concept is crucial in understanding how superconductors behave in the presence of magnetic fields, specifically through the London equations, which describe the electromagnetic properties of superconductors and explain how they expel magnetic fields through the Meissner effect.
congrats on reading the definition of Penetration Depth. now let's actually learn it.