Question

does Reflective index depends on optical density of the medium . what is the relation between the two

Answer 1

Optical density is the measure of the ability of the medium to allow the light to pass through. This can be synonymously used as refractive index of the medium. It is important to note that the refractive index of the material is not dependent of density (physical) of the medium.
By definition of the absolute refractive index of the medium, it is the ratio between the speeds of light in vacuum and the medium, if the optical density increases, the speed of light in the medium decreases.