. The refractive index describes the optical response of a material. (a) Consider a material with a single resonance at frequency v=v 0. Sketch the real and imaginary parts of the complex refractive index n(v) versus v, label the graphs, and describe the key features. (b) A liquid with refractive index n L=2.5+5.0i fills a plane parallel glass tank (inside width 1.0 cm,n G=1.5 ). Light with wavelength λ 0 =500 nm is normally incident on the tank. Find the reflection coefficient for a glass-liquid interface, the fraction of the incident light energy absorbed by the liquid, and the fraction of the light energy transmitted through the tank (ignore the airglass interfaces).