教师在做演示实验时，必须以准确无误的物理现象，展现在学生面前，让每个学生都能看清楚，才能使学生确信定律、概念的客观性，从而完成教与学的双边任务．然而，在实际的教学过程中，许多的演示实验细微处、关键处，学生无法看清，如力学实验中需读出弹簧秤的示数、萘的熔解 When teachers are doing demonstration experiments, they must be presented in front of the students with accurate and accurate physical phenomena, so that each student can see clearly, so that students can be convinced of the law, the objectivity of the concept, thus completing the bilateral tasks of teaching and learning. However, in the actual teaching process, many demonstration experiments are subtle and critical, and students cannot see clearly. For example, in the mechanical experiment, the reading of spring scales and the dissolution of naphthalene are required.