Over a perfect electrical conductor, boundary conditions force the tangential electric field to vanish at the surface, which causes the reflected electromagnetic field to become purely in-phase with the primary field (no phase lag), collapsing the generally elliptical polarization of the total field into a linear (straight-line) polarization, with the out-of-phase (quadrature) component of the response reducing to zero.
For electromagnetic induction over a general (finite-conductivity) subsurface target, the induced secondary field is generally out-of-phase (has a quadrature component) relative to the primary field,...
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