A parallel plate condenser is filled with two dielectric as shown in fig. Area of each plate is A metre2 and the separation is d metre. The dielectric constants are K1 and K2 respectively. Its capacitance is farad will be

The combination is equivalent to two capacitors in parallel each with plate area A/2 and separation d. See fig.Thus,  C1=K1εe(A/2)d=K1ε0A2d           C2=K2ε0(A/2)d=K2ε0A2dThe equivalent capacitance C is given byC=C1+C2=K1ε0A2d+K2ε0A2d=ε0AdK1+K22