本文将光视为电磁波，采用电动力学的方法，从施加外磁场的各向同性介质中的电子运动方程入手，分析磁场带来的变化，进而得到相对介电张量，之后结合麦克斯韦方程组解出本征态.该方法只需利用简洁的电动力学知识，便可以严格地导出磁致旋光体系的本征态必为右旋和左旋偏振态.相比传统方法，此推导能够使相关学习者更清晰地从本征值问题的角度理解磁致旋光效应的来源.

magnetic field to an isotropic medium will induce the optical rotation property. In this

paper， light is regarded as an electromagnetic wave. By using the method of electrodynamics，

starting from the equation of motion of electrons in an isotropic me- dium under an external

magnetic field， the change of the system caused by the magnetic field will be analyzed. And then

the relative dielectric tensor is obtained， which is solved by combining with Maxwell

equations. By using the simple knowledge of electrodynamics， we can strictly deduce that the

eigenstates of magneto-optical system must be right-handed and left-handed polarization.

Furthermore， we can make readers better understand the source of fara-

day effect in the perspective of eigenvalue problem.