How does the electric field behave near a charged surface? There is no obvious reason for the electric field to be the same on both sides of the surface. Using an infinitesimally small Gaussian surface and an infinitesimally small Amperian loop, you should explore how the electric field changes across a surface charge density. Do not assume that the surface is flat or has any special symmetry. It will help to look separately at the component of the electric field parallel to the surface $\EE_\parallel$ and the component perpendicular to the surface $\EE_\perp$.