利用幻灯进行教学,在我国正在逐步推广,我国正在准备按照生物教材的章节制作幻灯片。在教学中运用幻灯的结果,可使学生得到深刻的印象,在教学的实践中也证明这样做可以提高学生在生物方面的成绩,在初中尤为重要。但目前尚有许多生物教师对幻灯的构造及使用还不很清楚,现在简单地介绍一下: 一、幻灯机的一般原理幻灯机的主要构成部分,就是透镜和光源。它们的位置和关系如图1: (一)光源光源的作用就是用它发光去照明幻灯片,并把片上的影像透射到幕上。为了使影像清晰明 The use of slide for teaching, is gradually being promoted in our country, and our country is preparing to make slides according to the chapters of biological teaching materials. Students can get a deep impression by applying the result of slideshow in teaching. In teaching practice, this also proves that doing so can improve students’ biological achievements and is especially important in junior high schools. But there are still many biological teachers on the structure and use of the slide is not very clear, and now briefly introduce: First, the general principle of the slide projector The main components of the slide projector is the lens and light source. Their location and the relationship shown in Figure 1: (A) light source The role of the light source is to use it to illuminate the slide, and the image on the film transmitted to the screen. In order to make the image clear