theory of Electromagnetic Field的用法和样例：
例句
- This chapter provides the main background for the electromagnetic theory used in this book.
本章阐述本书所用的电磁场理论的主要基础。 - Based on the classical theory of electromagnetism, the relation and the difference between OAM and the parameter of the beam in paraxial approximation are analyzed.
从经典电磁场理论出发，主要介绍了傍轴近似条件下，光束的轨道角动量和光束的参数之间的关系。
