I'm trying to understand how electromagnetic radiation is created and can propagate through the void. I do understand the concept of an electromagnetic field. But I don't understand how we get from a "field" to a "wave".
I'm not really interested in detailed mathematics of how this happens, rather I'm looking for a complete high-level answer that to the extent possible:
- Explains every step of how we get from having nothing to having an electromagnetic wave that propagates through space (e.g wifi signal) and
- Provides clear and intuitive justification for any point/law/fact it uses.
Preferably all of this should be included within the answer but I do appreciate inclusion of helpful links and references for additional context.
Below is my current understanding along with some more specific questions.
To create electromagnetic radiation:
- You make some charge move (e.g through an antenna by creating an oscillating dipole).
- This moving charge creates fluctuating electric fields and magnetic fields around it
- All good so far as this is what you expect a charge to do, however these fields will become weaker proportional to inverse square of the distance and you would expect them to basically disappear at a distance.
- Electric and magnetic fields somewhat magically interact and now you have a self-perpetuating wave that doesn't fade out like the field.
I don't understand this part, e.g how we get from a "field" to a "wave" and unfortunately most of the resources I tend to skip over why. I believe there should be a better explanation.
For example, according to Wikipedia, Faraday/Len/Lorentz laws have to do with this. However all these laws/theories require a conductive "circuit" that we don't have in the air in the vacuum of space (I do understand how these laws explain how your antenna would receive an electromagnetic signal).
Considering magnetic and electric fields/forces will act on charged particles, this raises a few questions:
- Does the magnetic field produced by the antenna somehow create charge in the air surrounding it?
- If the whole wave propagation is based on interactions between the fields and charged particles, then how can a wave propagate through the void of space when there is no charge?