For the electromagnetic field generated by local sources, near and far fields are two key concepts which are introduced according to the characteristic wavelength. On the other hand, human understanding of electromagnetic fields has undergone a leap in understanding, from initially discrete static electric/magnetic fields to the complete moving electromagnetic fields described by Maxwell's equations. A finite temporal frequency is a significant characteristic quantity of dynamic field. This paper takes radiation sources of different dimensions as examples to analyze their near-field and far-field generation, distinguish the two mechanisms of near-field generation, and explain the relationship between near-field and static field. Finally, taking Fabry-Perot resonance in dielectric flat plates and surface plasmon resonance of metal particles as examples, the contribution of near-field energy storage in different dimensions and its direct relationship with the significant differences in quality factors of microcavities in different dimensions were revealed.

Rainbow is a common atmosphere optical phenomenon. In certain weather conditions, additional color arcs may appear near the main rainbow, which are called supernumerary rainbows. So far, there are few reports on the experimental research of the supernumerary rainbows. In this paper, we study the supernumerary rainbows from two aspects of both the collective scattering and individual scattering. The supernumerary rainbows phenomenon was reproduced by water mist light scattering, and the influence of the size and distribution of the water drops on the supernumerary is discussed. Then, through the light scattering experiment of single water drop, the phenomenon of supernumerary rainbows under different illumination wavelengths and different water droplet sizes is studied, and the formation mechanism of the supernumerary rainbows is explained from the micro level. We also use the Mie scattering theory to calculate and study the influence of the droplet size and its statistical distribution on the supernumerary rainbows phenomenon, and the calculation results further are consistent with the experiment ones.