Chern-Simons (CS) theta-systems are described by a theta integral F boolean AND F term in the action (theta is an adimensional parameter), which does not change field equations in the bulk, but affects the system behavior when it is bounded. When two of those theta-systems, each one characterized by a different value of. (even zero), share a common boundary, surface effects are then induced by a CS. term. Here, we study the consequences of the above in the propagation of electromagnetic radiation in theta-systems. In a previous paper, electromagnetic radiation properties traversing a theta-vacuum were analyzed, where a number of interesting features arise related to polarization and energy distribution. Now, we investigate how electric and magnetic properties of the theta-system affect the optical response. Apart from the well-known Kerr polarization rotation found for the particular case of topological insulators, we examine in detail the issue, and the results could be applied in other contexts where the theta term accounts for the system dynamics. In particular, we find two different Brewster angles, for s and p polarization of reflected radiation, respectively, with peculiar features derived from the. term influence. Possible applications of these results are discussed.