Asquare flat sheet of charge having uniform, charge per unit area. and side length d is aligned with the x-y axis of a cartesian coordinate system such that the center of the sheet is at the origin of the coordinate system. a closed spherical gaussian surface having radius r < d is positioned with its center at the center of the flat sheet. thus, the sheet divides the closed gaussian surface into two open hemispherical surfaces including a first hemispherical open surface that extends toward the positive z direction and a second hemispherical open surface that extends towards the open surface in terms of σ and r.