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于1994年秋开始使用的人民教育出版社物理室编中师物理课本第一册第37页上指出,凸透镜在屏上所成实像的亮度“跟会聚的光的多少有关。如果透镜比较大,会聚的光比较多,像就比较亮;如果用不透明体把透镜挡住一部分,会聚的光比较少,像就比较暗,但像仍是完整的。”这些内容尽管在历来的初等物理课本中很少明确提出,但常常由教师补充,从而有助于理解大物镜望远镜进光多,成像亮,就能观察到较多的暗星。该课本第38页上接着又指出,在用眼睛直接观察由凸透镜形成的虚像时,“如果把透镜遮住一部分,使进入眼中的光线减少,虚像的亮度也减弱,但像仍是完整的。”这个结论如此明确地出现在初等物理课本中尚属首次,值得探讨。
The page 37 of Book 1 of the Physics Division of the Physics Division of the People’s Education Press Physics Room, which began to be used in the fall of 1994, states that the brightness of the real image formed by the convex lens on the screen “is related to the amount of light that converges. If the lens is large, it converges. The light is more, and the image is brighter; if the lens is blocked by an opaque body, there is less converging light, and the image is darker, but the image is still intact.” Although these contents are rarely found in historical elementary physics textbooks. Clearly proposed, but often supplemented by teachers, which helps to understand the large objective telescope into the light, imaging bright, you can observe more dark stars. On page 38 of the textbook, it was also pointed out that when observing a virtual image formed by a lenticular lens directly with the eye, "if the lens is partially covered so that the light entering the eye is reduced and the brightness of the virtual image is also reduced, the image is still intact. This conclusion is so explicit in the textbook of elementary physics for the first time that it is worth exploring.