This book starts with the theoretical back ground of optical absorption in semiconductors. Various optical parameters like the absorption (A), transmission(T), extinction coefficient (K), refractive index (n),optical energy gap (Eg), etc. were calculated with detailed analysis of UV-VIS-IR spectra for ZnTe thin films deposited by successive ionic layer absorption and reaction (SILAR) method at various thickness and annealing temperature.The results are analyzed and discussed in detail in this book.