Question

What is the effect on the electrostatic force between charged bodies when dielectric slab is introduced between them?

Answer 1

the force is reduced by the factor of dielectric constant of the material that is intended between the charged bodies.

if initial electrostatic force = F
and dielectric constant of the material = K

then, electrostatic force between the bodies = F/K

according to Coulomb's law

force between two charged bodies kept in vacuum at a distance of r =
$\frac{1}{4\pi \: e} \times \frac{q1 \times q2}{ {r}^{2} }$
if the medium between the bodies has dielectric constant K,
then force =
$\frac{1}{4\pi \: ek} \times \frac{q1 \times q2}{ {r}^{2} }$