Why are EM waves blocked by non-conductors?

[Jocko Homo]

My father-in-law uses a USB internet stick for his internet since he lives in The Middle of Nowhere where there is no cable nor DSL. His problem is that reception from his basement office is very poor. However, reception from the second floor of his house is okay...

I don't understand this. What is blocking the reception of the stick? This is a phenomena I've seen many times. The most stark example is probably losing radio reception while driving through a tunnel. I've always assumed that it was the steel reinforcements of the concrete that acts as a Faraday cage to block radio reception but that theory doesn't work for this house. According to my father-in-law, the concrete foundation of the house is nothing but concrete...

Also, many GPS devices can't be used indoors, despite the walls and roofs of a house not being conductors. So, it would seem that my theory of EM blockage is flawed. In which case, how are the EM signals being blocked?

Thank you...

 

[Drakkith]

A conductor is not the only thing that absorbs EM radiation. Different wavelengths are absorbed differently by different materials. (Wow, different used 3 times in one sentence) For example, Visible Light is EM Radiation, and it is absorbed by many many things that aren't conductors. Practically all EM radiation will be absorbed by any material if you make it thick enough. The simple answer here is that the materials that make up the house DO block the signals enough to make the devices not work.