An analysis is presented of a planar array of narrow conducting strips residing at the interface between two semi-infinite half-spaces and excited by an incident plane wave that is transverse magnetic to the strip axes. The analysis is based upon an integral equation formulation in which the kernels of the coupled equations reduce from Sommerfeld-type integrals to closed-form expressions when the permeabilities of the two half-spaces are equal. The restriction that the strips be narrow relative to wavelength in either medium results in an approximate expression for the self-coupling of each strip. The use of special basis functions to expand the current on each narrow strip leads to a finite-term power-series expansion for the self-coupling of each strip. Expansion of the mutual coupling between narrow strips and of the excitation in series of simple powers allows the formation of a matrix equation that is solved for the expansion coefficients. Induced currents are presented for arrays of various size. The method presented is very efficient for the analysis of arrays consisting of a large number of narrow strips.