We consider the problem of light scattering in a slab of cholesteric liquid crystal with the pitch which significantly exceeds the wavelength of light. The electromagnetic wave propagation and the Green's function are investigated for this medium basing on geometric optics approximation. The correlation function of the director fluctuations is calculated with the aid of the vector analog of the WKB approximation. A general approach to treatment of single light scattering in a stratified medium with smoothly varying properties based on the Kirchhoff method is developed. Angular and polarization dependencies of the single light scattering intensity as well as extinction of the mean field are analyzed. Unusual dependence of the light scattering intensity on the size of the system is found.