1. The problem statement, all variables and given/known data A uniform plane wave propagates in a non-dissipative medium in the positive z direction. The frequency of the wave is 20 MHz. A probe located at z = 0 measures the phase of the wave to be 98 degrees. An identical probe located at z = 2 m measures the phase to be -15 degrees. What is the relative permittivity (e/e0) of the medium. 2. Relevant equations k = w*sqrt(u*e) w = 2*pi*f wt - kz = a constant w is angle velocity, u is permeability, e is permittivity 3. The attempt at a solution wt = phase angle Phase angle = kz K2 = -15/2 = -7.5 w = 2*pi*(20*10^6) K2 = w*sqrt(u*e), solve for e (e2) e2 = 2.83 * 10^-9 F/m Now I'm stuck on how to get the other e since z = 0. I think this problem should be easy, but I'm not seeing something.