7 (a) What is the size of the electric field a distance of 3m from a +3C point charge? (b What would the size of the force be on +2nC placed in the electric field? 8 (a) In a thin infinite plane interface between two homogenous isotropic media, state the valid relations that must exist between Ei, E, and E for all time t'and for all points on the surface (diagram is necessary). (b) State the three conditions required for such valid relations to exist in 2 (a) above.