学了幻灯机原理及其示意图(初中第二册p.24),有的学生会有疑问:“幻灯片的图相文字一般是透明的,光线是从灯丝发出和反光镜反射的,并不是从幻灯片发出,放映出来的怎会是幻灯片的像?”“聚光镜也是凸透镜,究竟是一个放映镜头起成像作用还是聚光镜和镜头合起来起成像作用?” Learned the principle of slide projector and its schematic diagram (secondary school p.24), some students will have questions: "The slide text is generally transparent, light is reflected from the filament and the mirror, not from the slide How can a film be presented as a slide show?” “The condenser lens is also a convex lens. Is it a projection lens that functions as an imaging lens or a condenser lens and a lens that combine to form an image?”