refractivity vs refractiveness

refractivity and refractiveness both are nouns.

Word	Noun	Adjective	Verb	Adverb
refractivity	Yes	No	No	No
refractiveness	Yes	No	No	No

As nouns, refractivity and refractiveness are synonyms defined as:

refractivity and refractiveness: the physical property of a medium as determined by its index of refraction

refractivity (noun)	refractiveness (noun)
the physical property of a medium as determined by its index of refraction	the physical property of a medium as determined by its index of refraction