We investigate experimentally the light sensitive Belousov-Zhabotinskii reaction in a silica gel. We focus on two ways of deforming wavefront curvature. In the first one, deformation is imposed by projecting a light spot on the medium rendering refractive phenomena analogous to traditional glass lenses in linear optics. Cellular automata simulations of these `chemical lenses' are in agreement with experiments. The second type of deformation is not imposed on the system but spontaneous; it is due to an instability which is not yet completely understood and which modulates aperiodically the curvature of the wavefronts, causing `ripples'.