全国中学生物理竞赛中的光学赛题 ,有的是对常规光学元件进行改造 ,创设出新的情境 ;或者是对给定光学系统内的某个元件附加题设条件 ,从而使赛题具有较高的难度 .参赛选手在求解此类赛题时 ,若能利用题设条件进行等效处理 :将改造过的常规元件等效为某几个光学元件的组合体 ; Some of the competition topics in the national junior high school physics competition are the transformation of conventional optical elements to create new situations, or the addition of conditions to a certain element in a given optical system, so that the title has a higher degree of difficulty. If competitors can solve such problems, they can use equivalent conditions to perform the equivalent treatment: the transformed conventional component is equivalent to a combination of several optical components;