I have been reading a few papers regarding the estimation of the permittivity $\epsilon_{mix}$ of a mixture of materials of permittivities $\epsilon_1$ and $\epsilon_2$ (I am not a phisicist or a physics student either, btw). I have found that there are many models for estimating it.
Two of those models are:
- $\epsilon_{mix} = V_1 \epsilon_1 + V_2 \epsilon_2$ where $V_1$ and $V_2$ are the fractions of the total volume occupied by the original materials, being $V_1 + V_2 = 1$
- $\epsilon_{mix}^{0.5} = V_1 \epsilon_1^{0.5} + V_2 \epsilon_2^{0.5}$
My question is, should I use this formulae on the real and imaginary parts of the permittivities separately, or use them on the whole complex permittivites? Obviously, there is no difference in the first model because $\epsilon_{mix}$ is linear with respect to $\epsilon_1$ and $\epsilon_2$, but this is not the case with the second model.