ABSTRACT
The distinction between static electric and magnetic fields and those produced by time-varying charges and currents is that one must take into account the finite propagation speed of light. The fact that the time of emission is different from the time of detection is the basis for the existence of electromagnetic radiation. Sufficiently near the source, retardation effects can be neglected. On the contrary, far away from the source, retardation effects become important. This chapter discusses asymptotic potentials and fields, electric and magnetic fields for a wave propagating in a specific direction, and angular distribution of radiated power. The amount of energy flowing across a unit area per unit time is expressed by Poynting’s vector. The chapter discusses radiation by an accelerated charged particle, and orientation of acceleration at emission time to direction of observation based on Larmor formula. The radiation by use of the Lorentz gauge is also discussed.
