Two large thin metal plates are parallel and close to each other. on their inner faces, the plates have surface charge densities of opposite signs and magnitude $27\times {10}^{-22} C m^{-2}.$ The electric field $\overrightarrow{E}$ in region II in between the plates is

In region II both of electric fields will be in same direction,

As we know the electric field due to a uniformly charged infinite plate $=\frac{\sigma }{2{\epsilon }_0}$

$\therefore$The value of $E$ in the region II, in between the plates $\frac{\sigma }{2{\epsilon }_0}+\frac{\sigma }{2{\epsilon }_0}=\frac{\sigma }{{\epsilon }_0}$

$=\frac{27\times {10}^{-22}}{8.85\times {10}^{-12}} = 3.03\times {10}^{-10} N C^{-1}$