EMI is necessary to protect electronic equipment from extraneous EM fields and to provide a controlled emission free environment for reliable functioning of electronic equipment. In this paper, the specific roles of reflection and absorption in determining the total shielding efficiency of three layer electromagnetic shielding, as a function of the frequency and the thickness of each layer is discussed. In particular, the reflection, the absorption and the shielding effectiveness of Tb11Fe86Cr3-polyacetylene doped electro chemically with 80% by weight iodine-copper laminatein the 2-18GHz frequency range have been presented.