In this work, we investigate the effect of UV light irradiation on the dielectric parameters of the nematic liquid crystal (5CB) containing dispersed ZnO nanoparticles. With addition of nanoparticles, nematic LC's are promising new materials for a variety of applications in energy harvesting, displays and photonics including the liquid crystal laser. To realize many applications, however one must optimize the properties of liquid crystal and understand how UV light irradiation interacts with the nanoparticles and LC molecules in dispersed/doped LC. The dielectric permittivity and loss factor are discussed for the pure nematic LC and dispersed/doped system after, during and before UV light exposure. Dielectric relaxation spectroscopy was carried out in the frequency range 100 Hz-10 MHz in the nematic mesophase.