凸透镜的应用之一是制成幻灯机的镜头。幻灯机是根据2f>u>f时,凸透镜能成放大的实象的原理制成的。放幻灯时,幻灯片应如何放置?这个问题在许多书刊中均有出现。 [例1]由少年儿童出版社出版的《掌握学习法》物理第二册AB卷63页上有这样一道题:放幻灯时,想使银幕上出现放大的“F”字母,那么幻灯片正确的插 One of the applications of the convex lens is a lens made of a slide projector. The slide projector is based on the principle that the convex lens can be made into an enlarged real image when 2f>u>f. How should a slide be placed when the slideshow is turned on? This problem has appeared in many books and magazines. [Example 1] “Mastery Learning” published by the Children’s Publishing House, Physics Book II, Volume AB, page 63 contains the following question: When you slide a slide, you want to make an enlarged “F” on the screen, then the slide is correct. Plug