Data given is speed of light in a medium (v) = 1.5 x 108 m/s
And assume that speed of light in vacuum as c= 3 x 108 m/s
Then, absolute refractive index of the medium (n) = c/v
Hence, n= (3 x 108) / (1.5 x 108) = 3 / 1.5 = 2
Thus, the absolute refractive index of the medium is 2.