1. The problem statement, all variables and given/known data Calculate the reflection coefficient of copper for radio waves at frequency 50Ghz and yellow light (wavelength = 0.6 micrometers) 2. Relevant equations Reflection coefficient: R = E(r)^2/E(I)^2 = (1-n/1+n)^2 Where E(r) is the electric intensity of the reflected wave, E(I) is the intensity of the incident wave Also, refractive index, n, is given by n = c/v, where v is given by frequency x wavelength. n = (epsilon x mu)^1/2 3. The attempt at a solution The key variable appears to be the frequency (wavelength for the yellow light) which effects the refractive index of the copper material. My problem is linking the two together, because as stated in the above equations, I am aware of the relationship but can't pin down a definite relationship which allows me to calculate one from the other. Any attempt to re-arrange n = c/v fails as even if i break v down in frequency x wavelength, i still have 2 unknowns (refractive index and wavelength (for radio waves) and frequency (for yellow light).) Any help with this would be much appreciated, as once the refractive index is found then the first equation stated can be used. Many thanks.