Question

The index of refraction n for sapphire is 1.76. what is the speed of light in sapphire?

Answer 1

The index of refraction of a material is the ratio between the speed of light in vacuum and the speed of light in that material:

`n= (c)/(v)`
where
n is the refractive index

`c=3 \cdot 10^8 m/s` is the speed of light in vacuum
v is the speed of light in the material

For sapphire, n=1.76, so if we re-arrange the previous equation and we use this value, we can calculate the speed of light in sapphire:

`v= (c)/(n)= (3 \cdot 10^8 m/s)/(1.76)=1.7 \cdot 10^8 m/s`