摘要
薄透镜的等光程性在许多基础物理教材中仅给予了定性的说明，本文以空气中的薄透镜为例，分四种情况。
In many basic physics textbooks, the equal optical path of thin lens is only explained qualitatively. However,this has been proved quantitatively in four cases in this paper,provided that the thin lens is in air.
关键词
薄透镜
光程
近轴光线
thin lens
optical path
axial ray
