  Domains of finite topological charge density can exist in chiral materials
and chiral matter. Spatial and temporal variation of the average topological
charge density, represented by the $\theta$-field, induces anomalous currents
that are responsible for the chiral magnetic effect, the anomalous Hall effect
and other phenomena that are intimately related to the chiral anomaly. We
consider domains with constant average topological charge density. We argue
that even though the Maxwell equations in the bulk are not altered, the chiral
anomaly manifests itself by the way of the boundary conditions. This is
illustrated by several examples. The first example deals with the refraction of
plane electromagnetic wave on a surface of a constant-$\theta$ domain. We
derive the modified Fresnel equations and discuss the effect of the chiral
anomaly on the amplitude and polarization of the reflected and transmitted
waves. In particular, we argue that the Brewster's angle is sensitive to the
value of $\theta$. In the second example we compute the spectrum of the
transition radiation at high frequencies and show that it is enhanced at finite
$\theta$.
