Index of refraction
When light travels from one material to another it usually changes direction
The bending of light that occurs at the borderline of two materials is called refraction
the amount of bending depends on the optical properties of the two materials --> characterized by their index of refraction: n
n is a number: n=1 for vacuum, n=1.33 for water, n=2.42 for diamond, n=1.5-1.9 for different types of glass …….
when the amount of bending is bigger, the difference in n is bigger for the two materials
-normal to the point of incidence