Answer:

Relation between polarization P, Susceptibility $\chi$ and $\in_{r}$:

Consider a parallel plate capacitor with plates between which an electric field $E_{0} $exists. If $\sigma$ is the change/unit area then using gauss law.

$E_{0} = \dfrac{\sigma}{ E_{0} }$ …………………………….(1)

Let the dielectric slab be placed between the two plates. …