In an absorbing medium, the reflective index becomes a complex number: πΜ = π β² + ππ β²β². Assume that a plane wave πΈβ (π₯,π‘) = πΈβ 0π βπ(ππ‘βππ₯) is incident on this medium. (a) Starting from the plane wave dispersion in a medium (Ο = π π π), show that the field intensity (|πΈ| 2 ) decreases exponentially over distance (i.e. |πΈ| 2 β e βπΌπ₯). (b) Express the absorption coefficient Ξ± in terms of other parameters.