Electromagnetic radiation penetration through solids?

[xr250h]

So I'm doing a presentation soon discussing the horribly inaccurate physics of the movie "The Core", and in particular how they were able to maintain radio contact to people on the Earth's surface from within the center of Earth.

This is obviously simply not possible as radio waves do not like to penetrate rock very well, let alone penetrate it for 5000 km. What I can't seem to find are equations that can show this.
Ideally, I'd like to find an equation(s) that will allow me to plug in a given wavelength of EM radiation, the density of the object, and get either a penetration depth, or an intensity.

Do such equations exist?

 

[Vailanor]

Yes, there are equations that can be used to calculate the penetration depth of electromagnetic radiation into a material. The most commonly used equation is the Skin Depth Equation, which states that the penetration depth is inversely proportional to the square root of the frequency and the conductivity of the material. The equation is given by: Penetration Depth = $\sqrt{\frac{2}{\mu \omega \sigma}}$ Where $\mu$ is the permeability of the material, $\omega$ is the angular frequency of the radiation, and $\sigma$ is the electrical conductivity of the material. This equation can be used to calculate the penetration depth of any given EM radiation, given the material properties of the medium it is passing through.