We know that electromagnetic radiation is propagated when an excited electron orbiting a nucleus collapses from a higher orbit to a lower orbit or a higher state of energy to a lower state of energy thereby giving off light.
How well do we understand the process? Do we now understand exactly what’s taking place?
Do we know the shape of light quanta when propagated? Do we understand the reason for the speed of light? And how and why the speed takes place? Can we understand the starting energies and the energies of quanta after many years in space and of the ever-increasing size of light as it travels through space?
Is there an article, study or book that deals with electromagnetic propagation that could explain or explore this subject in detail?
Any reading material recommended would be appreciated.