Optical studies are done on Poly methyl-methacrylate (PMMA) sheets. Samples were previously prepared by catalytic chain transfer polymerization via metal carbazone of Cd(II) and Hg(II). Transmission and absorbance are recorded (between 190 nm to 1100 nm) as a function of incident energy using UV-VIS spectrophotometer. Second derivative of absorbance spectra is calculated to enhance differences among spectra. The optical band gap, width of band tail and dispersion of refractive index of the sheets are determined.