Initially the space between the plates of the capacitor is filled with air, and the field strength in the gap is equal to E 0. Then half the gap is filled with uniform isotropic dielectric with permittivity e as shown in Fig. 3.12. Find the moduli of the vectors E and D in both parts of the gap (1 and 2) if the introduction of the dielectric?
(a) Does not change the voltage across the plates;
(b) Leaves the charges at the plates constant.

1