Question

The speed of light in a leaded glass is 1.66x10^7 m/s. What is the index of refraction of this type of glass? 

Answer 1

The index of refraction

$$n=\frac{c}{v}=\frac{3.00*10^8\:\rm m/s}{1.66*10^7\:\rm m/s}=18.1$$