Abstract:

Rainbow is a common natural phenomenon. In optical teaching，Fermat principle

is the general method for rainbow angle deduction. Nevertheless，this paper explores the

principles and features of rainbow from the perspective of wave optics by calculating the

intensity of the primary and secondary rainbow quantitatively using Fresnel formula.

Furthermore，we give the theoretical explanation of the rainbow angle and prove that

rainbow is partial polarized light.

Key words: rainbow, wave optics, Fresnel formula, polarization, Fermat principle