The optical constants, thicknesses and densities of thin titanium oxide films, deposited by electron beam evaporation, were measured. The variation of the refractive index with the density, of titanium oxide samples in the form of thin films (present work) and bulk crystalline form (data from the literature), was observed to follow the Lorentz-Lorenz law. The molecular electronic polarizability deduced from the law was close (within the uncertainty in the measurement) to the value reported in the literature. Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy studies were carried out on the thin films.