Derivation of reflectivity

outplayed

1. The problem statement, all variables and given/known data
Considering a wave traveling in air (permittivity and permeability 1), when the wave hits the surface of a solid, there is a reflected wave back into air, and a transmitted wave into the material. Assuming the material has a permeability of 1 and the wave hits the material at normal incidence, derive an equation for the reflectivity in terms of the index of refraction of the material and extinction coefficients.


2. Relevant equations
B = √(εμ) * E where ε is the permittivity and μ is the permeability
n = √(εμ)

3. The attempt at a solution
I believe that this has something to do with the Fresnel equations, though i'm not too familiar with them. Otherwise i'm not sure where to begin with this. I don't see how to relate E and B to refractive index and extinction coefficients.