So I’ve been trying to comprehend how wifi works, and just cannot visualise it.
I know that there is this field were surrounded by, and antennas create waves in it that can be picked up by other antennas.
I’ve been trying to visualise it similar to being underwater and moving water around with your hands, but not sure if this is accurate.
Anyway, I don’t know what this “field” is made of. Can someone ELI5?
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All things that are called “waves” satisfy the wave equation. The wave equation tells how a field change over time. While there are significant differences depending on the space and the type of quantity, because of the shared mathematical equation, you can often visualize one field using another, as long as you’re aware of the difference and don’t carry them over.
For example, when you create pressure wave in water (aka. sound wave), these are longitudinal wave, which is different from transverse wave, in that the water move along the direction you push, not perpendicular to it. But as long as you know that, you can still think about the amplitude of the wave and they are still the same.
So first, let me talk about EM field.
A “field” is a mathematical model that assign each point in space a quantity. The “space” could be literal space, or smaller part of space, spacetime. “Quantity” are things that can be added, scaled and subtracted, which does not have to be just numbers.
Height of water over the water surface is a field: here the “space” is the 2-dimensional water surface, and the “quantity” is a number for height. Direction of air flow is a field: the “space” is the 3-dimensional space where air occupy, and the “quantity” is the 3-dimensional vector telling you where and how much air flow. You will see that physics frequently will use fields to describe things.
So what is EM field? There are actually 2 versions of it. The non-relativistic EM field is a field in which the “space” is 3-dimensional space everywhere, and the “quantity” is the pair of vectors describing electric and magnetic field. The relativistic EM field is a field in which the “space” is the 4-dimensional spacetime, and the “quantity” is a function that tells you density of “flux” through an infinitesimal “surface” in spacetime.
Let me emphasis that they’re both *mathematical model* about how electromagnetism work. Neither are accurate, but they’re very good most of the time. Non-relativistic EM field are easier to visualize and works well in everyday situation, while relativistic EM field is more accurate at high velocity situation. None of them are how physics “really” work.
So does the “pressure wave in water” picture you have been using work? Yes. For the question you have (how do I transmit information with wave on a field?), the analogy using water work just fine.
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