Why are EM waves blocked by non-conductors?

In summary, the problem of poor reception for a USB internet stick in a basement office can be attributed to the materials of the house blocking the EM signals. Despite the walls and roofs of a house not being conductors, different materials can still absorb EM radiation at different wavelengths, leading to interference and loss of signal. This can also explain why GPS devices may not work indoors, as materials in the house can absorb the EM signals, rendering the devices unusable.
  • #1
Jocko Homo
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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...
 
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  • #2
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.
 

FAQ: Why are EM waves blocked by non-conductors?

Why do non-conductors block EM waves?

Non-conductors, also known as insulators, block EM waves because they do not allow the flow of electric charges. EM waves are made up of oscillating electric and magnetic fields, and conductive materials allow these fields to pass through them due to the presence of free electrons. Non-conductors, on the other hand, do not have free electrons and therefore cannot support the flow of electric charges, causing them to block EM waves.

Can any material block EM waves?

Yes, any material can block EM waves to some extent. However, the degree to which a material can block EM waves depends on its conductivity. Highly conductive materials, such as metals, are very effective at blocking EM waves, while insulators are less effective.

How does the thickness of a non-conductor affect its ability to block EM waves?

The thickness of a non-conductor does not have a significant impact on its ability to block EM waves. As long as a material is a non-conductor, it will block EM waves regardless of its thickness. However, a thicker material may provide more barriers for the EM waves to pass through, making it slightly more effective at blocking them.

Are all non-conductors equally effective at blocking EM waves?

No, not all non-conductors are equally effective at blocking EM waves. The effectiveness of a non-conductor in blocking EM waves depends on its dielectric constant, which is a measure of how much the material can polarize in response to an electric field. Materials with higher dielectric constants are more effective at blocking EM waves.

Can EM waves pass through a vacuum?

Yes, EM waves can pass through a vacuum. In fact, EM waves are able to travel through empty space at the speed of light. This is because a vacuum does not contain any particles or atoms that can interact with the electric and magnetic fields of the EM waves, allowing them to pass through without any obstruction.

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