彩虹是一种常见的自然现象.在光学教学中，通常用费马原理推出彩虹角.而本文从波动光学出发探究彩虹的原理与特征，运用菲涅耳公式定量计算出主虹与副虹的光强，从而给出彩虹角的理论解释，并利用计算结果证明彩虹是高度偏振的部分偏振光.

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.