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Thank you for answering me, you can see here the way Feynman did http://www.feynmanlectures.caltech.edu/I_29.htmlstevendaryl said:I think you're getting off track. There are two types of electromagnetic fields: static and propagating. If I have a charge ##Q##, it has an associated static electric field: ##E = \frac{Q}{r^2}##. It does NOT propagate like a wave. It's constant. Similarly, a constant current density such as a current-carrying wire will produce a static magnetic field. That doesn't propagate as a wave, either.
But in empty space, far from any charges, you can still have an electromagnetic field. A changing electric field acts a "source" for the magnetic field. Similarly, a changing magnetic field acts a source for the electric field. So if both the electric field and magnetic field are changing, they can create a self-sustaining wave.
You can't derive that fact from Coulomb's law for static fields (or at least, I don't know how, maybe Feynman did).
Thank you for being so kind. I really like your answer.BvU said:Hi Adesh, ,
I looked at the lecture and see that Feynman concentrates on ##(t-r/c)## to reason the disturbance propagates outward with speed ##c##. As you calculate, the amplitude diminishes with ##r##, so you get a similarity and not an exact equality.
The ##1/r## has to do with the energy radiated, that has to be distributed over an area that increases with ##r##. As Feynman explains much more clearly in 29.2
So: kudos for your efffort , point taken, but: read on !
One of the main pieces of evidence is the observation of interference patterns, which is a characteristic of waves. This has been observed in experiments involving electric fields, confirming their wave-like behavior.
The speed of an electric field wave can be measured by dividing the distance between two points by the time it takes for the electric field to travel between them. This is known as the propagation speed and is found to be approximately equal to the speed of light.
Yes, electric field waves can be polarized, meaning the direction of their electric field oscillations can be controlled. This is commonly seen in everyday technology, such as polarized sunglasses, which use this property to reduce glare.
The wavelength of an electric field wave determines its energy and frequency. A shorter wavelength corresponds to a higher frequency and energy, while a longer wavelength corresponds to a lower frequency and energy. This can affect how the wave interacts with matter and other waves.
Yes, electric field waves can interfere with each other, either constructively (when they add together) or destructively (when they cancel each other out). This phenomenon is key in understanding the behavior of electric fields and is often observed in experiments.