Electric field applied in a dielectric material My physics book introduces dielectric materials by considering firstly the electric effects due to polarization (without taking into account the causes of this polarization). Then the book itself considers the determination of polarization as a consequence of the field acting on the material. In particular, it is said that the determination of the field itself is complicated because the field which produces the polarization does not derive only from the charges we put on the different bodies immersed in the dielectric material but also from the effects of the polarization itself of the dielectric material.
I am not sure why this is true. I guess the electric field applied to the dielectric material does not depend on the polarization effects but the book seems to state this.
 A: When a component of a dielectric gets polarized, it creates a field of a dipole. This field alters the polarization of the dielectric around it. This has many non-trivial effects. For example, lets say we have a charge by 2 dielectric slabs. The field of the charge will create image charges in both dielectrics. These image charges will then create their own mirror charges in the other dielectric. This process continues indefinitely. The end result would be an infinite string of image charges. As such, the field of such a simple system is complicated.
Edit: For simplicity, lets think of a person standing between 2 mirrors. The mirror act like dielectrics with infinite permittivity. The mirror charge would always have the opposite charge as the charge itself. Now, for a person standing between 2 mirrors, they will see their reflection, their reflection's reflection, and so on and so forth. The end result is a person sees and infinite line of themselves. If we did this in the case of a charge, the charge would see an infinite line of charges with alternating charge. As such, it'd create a complicated electric field.
