中文说明：
passion方程的第一类边界条件的数值解，边界条件过于复杂而无法求得解析解。这就需要借助于数值法来求电磁场的数值解。有限差分法便是一种比较容易的数值解法。
English Description：
The numerical solution of the first boundary condition of the passion equation is too complex to obtain the analytical solution. This requires the help of numerical method to find the numerical solution of electromagnetic field. The finite difference method is an easy numerical method