The conventional integral equation governing the electric field inside
dielectric particles is reformed to bridge and to protide mathematica
l foundations for analytic techniques widely used to estimate such a f
ield. The solution of the reformed equation inside a dielectric slab e
xplained ho cv inner-field formulations based on the Rayleigh, the Ray
leigh-Gans, the quasi-static, and the Shifrin approximations can be su
pported by the particles. It also confirmed the approach employed to r
eform the integral equation. The analysis performed uncovered the diff
erences between the depolarization tensor characterizing electrostatic
fields inside the particles and the source dyadic resulting from the
extraction of the singularity of the integral equation kernel. (C) 199
7 Optical Society of America.