When light passes from one medium (material) to another it changes speed. This is because the speed of a wave is determined by the medium through which it is passing. When light speeds up as it passes ...

We can also use wavelengths to calculate refractive index. By substituting \(v_{1}=f\lambda _{1}\) and \(v_{2}=f\lambda _{2}\) into \(n=\frac{v_{1}}{v_{2}}\) then ...