本文基于几何光学和柯西色散公式，对虹霓这一大气光学现象形成原因进行了完整的探究，对虹的最大视角和霓的最小视角做出了说明.同时设计了一套可以再现虹霓现象的装置，并给出了一种基于平行原理间接测量虹霓各色光视角的方案.实验中通过改变NaCl溶液浓度测得虹与霓的红光视角，将其与理论值在图像上比对后发现二者较好地吻合，说明虹霓现象出射光强确实集中分布于最大视角处，同时也说明柯西色散公式适用于计算NaCl溶液对不同色光的折射率.

Based on geometric optics and Cauchy dispersion formula, this paper completely explores the reasons for the formation of the atmospheric optical phenomenon of rainbow neon, and explains the maximum viewing angle of rainbow and the minimum viewing angle of neon. At the same time, a device that can reproduce the rainbowni phenomenon is designed, and a scheme for indirectly measuring the light viewing angle of each color of the rainbowneon based on the parallel principle is given. In the experiment, the red light viewing angle of rainbow and neon is measured by changing the concentration of NaCl solution, and compared it with the theoretical value on the image, and found that the two were in good agreement, indicating that the intensity of the emitting light of the rainbow neon phenomenon is indeed concentrated at the maximum viewing angle. At the same time, it also shows that the Cauchy dispersion formula is suitable for calculating the refractive index of NaCl solution.