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.