refractive

a. [ Cf. F. réfractif. See Refract. ] Serving or having power to refract, or turn from a direct course; pertaining to refraction; as, refractive surfaces; refractive powers. [ 1913 Webster ]

Refractive index. (Opt.) See Index of refraction, under Index. --
Absolute refractive index (Opt.), the index of refraction of a substances when the ray passes into it from a vacuum. --
Relative refractive index (of two media) (Opt.), the ratio of the sine of the angle of incidence to the sine of the angle of refraction for a ray passing out of one of the media into the other. [ 1913 Webster ]