Polydomain nematic sheets can be designed for desired shape transition, and a typical example is a disc composed of congruent wedges with rank-1 connected director field. Recent theoretical study indicated that such a disc, if infinitesimally thin, tends to become a perfect pyramid upon illumination. Nonetheless, what is the influence of the finite thickness remains unexplored. In the present work, we reexamine this problem by treating the disc as an elastic plate with finite thickness. Analytical solution to the photo-actuated shape is obtained in small deformations, and the influences of the number of domains and the attenuation of photo intensity are discussed in detail. The results are expected helpful to the design of related photo-responsive devices.