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书写投影仪的作用之一就是能将细小的物体或变化作投影放大,笔者在教学中巧用这一特点,成功地做了两个演示实验.一、投影演示液体的蒸发现象在投影仪的书写面板上放一块洁净的透明玻璃,打开电源,然后用滴管滴一滴乙醚在玻璃上,由于光的折射,影幕上将会出现放大的液滴.随着蒸发的进行,液滴很快(十几秒钟)逐渐收缩变小,最后成一点后突然消失.附近的同学还可嗅到刺激的气味.这样把平缓进行的蒸发现象,投影放大在学生面前,使学生看得见,“嗅”得着.
One of the functions of the writing projector is to enlarge the projection of small objects or changes. In the teaching, the author skillfully used this feature to successfully make two demonstration experiments. First, the projector demonstrates the evaporation phenomenon of the liquid in the projector. Put a clean transparent glass on the writing panel, turn on the power, and then drop a drop of ether on the glass with a dropper. Due to the refraction of light, an enlarged droplet will appear on the screen. With the evaporation proceeding, the droplet will soon (More than ten seconds) gradually shrinks and becomes smaller, and finally disappears after becoming a little. Nearby classmates can also smell the stimulating odor. This will magnify the gradual evaporation phenomenon and enlarge the projection in front of the student so that the student can see it. “Smell!”