“义教版”初中物理第一册，有个海波熔解的演示实验。这个实验按照教材装置去做，难以取得良好的效果，究其原因有两个：一是学生看不清楚温度计的示数；二是学生看不清楚晶体的状态变化情况。教师在台上精心演示，学生在台下无所事事，教学效果差。但是，只要增加一台投影仪 In the first volume of junior high school physics, there was a demonstration experiment of the sea wave melting. This experiment is done according to textbooks and it is difficult to obtain good results. There are two reasons for this: First, students cannot see the thermometer’s readings. Second, students cannot see the state of crystals. The teacher carefully demonstrated on the stage. The students did nothing at the stage and the teaching effect was poor. However, just add a projector