what is the S,I unit of refractive Index - Physics -

Question

what is the S,I unit of refractive Index?

Abhishek Gupta · Accepted Answer

Dear Student
The refractive index or index of refraction of a substance is
a measure of the speed of light in that substance It is expressed
as a ratio of the speed of light in vacuum relative to that in the
considered medium
A simple, mathematical description of refractive index is as
follows:
<img height="38" width="214" src=
"https://s3mn%20mnimgs%20com/img/shared/userimages/mn_images/image/6_12_2%20png"
alt="">
Clearly, refractice index is a ratio and thus doess not have a
unit It is just a number

Best wishes!!