I was studying light as electromagnetic radiation in Feynmann's lectures book (Vol. 1, Ch. 28) and, in explaning how radiation works, he gives the following expression for the electric field at a point in space generated by a moving point charge :
In most references i could find, the expression for the electric field only takes the first term, which originates from Coloumb's law:
My questions then are, where does the expression given by Feynmann come from, or how can it be proved? And are there any references that give an explanation/derivation for it?
Thanks for the help.
References for the images:
(1) 28 - Electromagnetic Radiation. https://www.feynmanlectures.caltech.edu/I_28.html
(2) Electric Field due to a Uniformly Charged Ring. https://medium.com/swlh/electric-field-due-to-a-uniformly-charged-ring-6b0adcbf7b8d
