Capacitor

The distance between two plates of a capacitor is \(\mathrm{d}\) and its capacitance is \(\mathrm{C}_{1}\), when air is the medium between the plates. If a metal sheet of thickness \(\frac{2 d}{3}\) and of the same area as plate is introduced between the plates, the capacitance of the capacitor becomes \(\mathrm{C}_{2}\). The ratio \(\frac{\mathrm{C}_{2}}{\mathrm{C}_{1}}\) is