初中的光学演示实验要用到束光源。一般中学实验室里是用点光源通过凸透镜得到平行光后,让部分平行光通过狭窄的细缝而得到束光的。这样得到的束光亮度较小,白天在教室里演示效果不好。用激光器作为课堂中演示的束光源,是比较理想的。但激光器价格贵,使用寿命较短,保养也较为讲 The beam demonstration light source is used in junior high school optical demonstration experiments. In general high school laboratories, point lights are used to obtain parallel light through a convex lens, and then part of the parallel light passes through a narrow slit to obtain beam light. The brightness of the beam obtained in this way is small, and the demonstration effect in the classroom is not good during the daytime. Using a laser as a beam source for demonstration in the classroom is ideal. However, the laser is expensive, its service life is short, and its maintenance is relatively speaking.