Answer:
n = 1,429
Step-by-step explanation:
In this exercise you are asked to calculate the refractive index, it is a constant that depends on the wavelength and relates the behavior of light when passing through two different material media.
The refractive index of a material is given by
n = c / v
where n is the refractive index, c the speed of light and v the speed in the material medium
let's calculate
n = 3.0 108 / 2.1 108
n = 1,429