# High frequency limit of permitivity function

I am taking a course in solid state physics, and I have a question about the behavior of the (relative) permitivity function $$\epsilon_r (\omega)$$ for dielectric materials.

In the Drude model, we discover that electromagnetic radiation is attenuated in metals below a critical frequency, the plasma frequency, but that above this metal, they become transparent to electromagnetic radiation, and so $$\epsilon_r = 1$$.

My question is, what happens to the relative permitivity function for dielectric materials in this high frequency limit? Do dielectric materials become transparent like metals for sufficiently high frequencies of light?

I know that it is equal to the "optical permitivity" given by

$$\epsilon_{r,opt}$$ = $$\frac{N \alpha}{V \epsilon_0}$$,

where $$N/V$$ is the density of the dielectric and $$\alpha$$ is the atomic polarizability, but I cannot figure out if $$\epsilon_{r,opt}$$ actually approaches 1 for high frequencies, which would mean that dielectrics become transparent. I would have to know the atomic polarizability for the dielectric - is there a general expression for $$\alpha$$ valid for all dielectrics?