In a medium of dielectric constant $K$,the electric field is $\vec E$. If $\varepsilon_0$ is the permittivity of free space,the electric displacement vector is:

Give examples of polar and non-polar molecules.

$Assertion \; (A)$: Non-polar materials do not have any permanent dipole moment.
$Reason \; (R)$: When a non-polar material is placed in an electric field,the centre of the positive charge distribution of its individual atom or molecule coincides with the centre of the negative charge distribution.
In the light of the above statements,choose the most appropriate answer from the options given below:

What is a linear isotropic dielectric?

How does the polarised dielectric modify the original external field inside it?

Explain the polarization of a nonpolar molecule in a uniform electric field and define linear isotropic dielectrics.