  We consider two inverse boundary value problems for the time-harmonic Maxwell
equations in an infinite slab. Assuming that tangential boundary data for the
electric and magnetic fields at a fixed frequency is available either on
subsets of one boundary hyperplane, or on subsets of different boundary
hyperplanes, we show that the electromagnetic material parameters, the
conductivity, electric permittivity, and magnetic permeability, are uniquely
determined by these partial measurements.
