A point charge Q is located just above the centre of the flat face of hemisphere as shown in figure. The electric flux through the flat face and curved face of hemisphere are respectively

Place another identical hemisphere on given one, so that flat faces of two coincide. The total flux linked with cross- section of bottom half (lower hemisphere) is $\frac{\mathrm{Q}}{2{\mathrm{ϵ}}_0}$ as charge enclosed by given hemisphere is zero. So flux linked with flat face of hemisphere is $\frac{-\mathrm{Q}}{2{\mathrm{ϵ}}_0}$