Question

What is the speed of light with N=1.33

Answer 1

`v=2.25` 10^(8) (m)/(s)`
N=1.33 being the Index of Refraction of a material and
`c=3.0` 10^(8) (m)/(s)` the speed of light in vacuum you get:

`v= (c)/(N)= (3.0 10^(8) )/(1.33)=2.25` 10^(8) (m)/(s)` speed of light in that material.

Answer 2

If the refractive index of some substance is 1.33, then
the speed of light in that substance is

(speed of light in vacuum) / (1.33) =

(299,792,458 m/s) / (1.33) = 225,407,863 m/s