《毛细现象》一课中有这样一个实验 :玻璃细管插入水中后 ,水在玻璃管内上升 ,且管子内径越小 ,管中水面上升得越高。由于实验的可见度小 ,即使在前排的学生也难以看清 ,因此宜用投影器教学。但若按平常的做法 ,在投影器的聚光镜上做实验 ,玻璃管在银幕上的图像是一圆斑 ,根本 In the Capillary Phenomenon lesson there is an experiment where the glass tube is inserted into water and the water rises inside the glass tube and the smaller the tube inner diameter, the higher the water level in the tube rises. Due to the small visibility of the experiment, even in the front row of students is difficult to see, it is appropriate to use projector teaching. However, if the usual practice, in the condenser condenser lens experiment, the glass tube on the screen image is a circular spot, the fundamental