**Polarization of Dielectric Material:** Consider a parallel plate capacitor with +q and –q charges.

**Fig: Polarization of dielectric material**

Let E_{0} be the electric field between the plates in the air. If a dielectric slab is introduced in the space between them, the dielectric slab gets polarized. Suppose +q_{i} and –q_{1} be the induced surface charges on the face of dielectric opposite to the plates of the capacitor (Figure). These induced charges produce their own field E_{i} which opposes the electric field E_{0}. So, the resultant field, E < E_{0}. But the direction of E is in the direction of E_{0}.

so, **E = E _{0} + (–E_{i})**

(Here E_{1} is opposite to the direction of E_{0})