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一、在研究晶体和非晶体的物理性质时,书上有这样一个演示实验:在云母片和玻璃板上均匀涂上石蜡,用烧红的针尖去接触带有蜡一面的云母片和玻璃板,从而得到云母片上熔化的蜡形状为椭圆形,玻璃板上为圆形,但是椭圆和圆都非常小,学生看不到,演示效果差,我在教学中作了改进。用小钢珠代替针尖,具体做法如下:在云母片和玻璃板上均匀涂上石蜡,用烧红的小钢珠(直径3～5毫米左右)去接触云母片和玻璃板没有涂蜡的一面,等蜡凝固后,放在幻灯机上打到屏上,全班学生都能清晰地看到云母片上熔化的蜡为椭圆形,玻璃板上熔化的蜡为圆形,从而得到晶体表现为各向异性,非晶体表现为各向同性。
First, in the study of the physical properties of crystals and non-crystals, there is a demonstration experiment in the book: Uniformly smear paraffin on mica and glass plates, and use magenta tips to contact mica plates and glass plates with a wax side. Therefore, the shape of the wax melted on the mica plate is oval, and the glass plate is round, but the ellipse and the circle are very small, students can not see it, and the demonstration effect is poor. I made improvements in teaching. Replace the tip with a small steel ball, the specific approach is as follows: in the mica plate and glass plate evenly coated with paraffin, with red small steel ball (about 3 to 5 mm in diameter) to contact the mica plate and the glass plate is not wax coated side, etc. After the wax is solidified, it is placed on a slide projector and displayed on the screen. The students in the class can clearly see that the wax on the mica plate is elliptical, and the wax on the glass plate is circular, so that the crystal is anisotropic. Non-crystals behave isotropically.