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I've been reading about these topics (Feynman lectures and more on the internet and some books) but I still have a doubt, maybe because I haven't understood the whole of it.

This is my doubt: Think of an imaginary situation in which we have an accelerating charge. The electromagnetic field will change and the charge will emit radiation. As far as I know, a point which is 300,000,000 meters away form the charge won't feel the change until one second in the future, because of

*c*.

Now, what if, as it is seen in the picture, radiation suddenly "disappears" in an angle? Would the point A feel the change, if it is in that area of space without radiation?

(It is possible that electromagnetic waves could reach the point A by diffraction, so I extended the barrier with the purple lines which go to infinity) I also wanted to ask: if electromagnetic waves don't reach that point directly (because of the blue barrier) but they do by diffraction, would the electromagnetic field in that point of space be the same as if they did directly?

I'd be grateful if you could answer me in both situations: with just the blue barrier, and with both the blue and the purple.

Picture: https://ibb.co/foZ1Hv

White lines -> electromagnetic radiation.

Yellow point -> charge.

Blue line -> hypothetical barrier which absorbs radiation 100%

Purple line -> extended hypothetical barrier.

Thank you in advance.