With these ideas in mind, consider a slab of dielectric material placed between the plates of a capacitor so that it is in a uniform electric field XXX as shown in figure 26.21b. The electric field due to the plates is directed to the right and polarizes the dielectric. the net effect on the dielectric is the formation of an induced positive surface charge density O on the right face and an equal-magnitude negative surface charge density O on the left face as shown in figure 26.21c. Because we can model these surface charge distribution as being due to charge parallel plates, the induced surface charge on the dielectric give rise to an induced electric field O in the direction opposite the external field XX Therefore, the net electric field VVV in the dielectric has a magnitude.