A parallel-plate capacitor has square plates that are 8 cm on each side and 3.8 mm apart. The space between the
plates is completely filled with two square slabs of dielectric, each 8 cm on a side and 1.9 mm thick. One slab is pyrex glass ( dielectric constant = 4.7) and the other is polystyrene (dielectric constant = 2.6). If the potential difference between the plates is 86 V, how much energy is stored in the capacitor?
Draw diagram and explain physical principle of the problem and write mathematical expressions and solve the problem.