读者王驰卓问:“通过凹透镜的光线一定变成发散的光线吗?为什么凹透镜只能成缩小的像?”我们用透镜的成像公式可以简明地回答这个问题.为了正确使用透镜的成像公式,首先要对成像公式中的量的符号作出规定,图1表示一个凸透镜的成像.物AB在透镜L的左侧,说明光线由L的左侧射向L,图中的A′B′是AB的像,它在L的右侧.我们称L的左侧空间为物空间,而L的右侧为像空间. Readers Wang Chi Zhuo asked: “The concave lens through the light must become divergent light? Why concave lens can only be reduced to like?” We use the lens imaging formula can concise answer this question.In order to correctly use the lens imaging formula, first of all Figure 1 shows the imaging of a convex lens. The object AB is on the left of the lens L, indicating that the light is directed from L on the left to L, and A’B ’in the figure is AB Like, it is to the right of L. We call the left space of L the object space, and the right of L the image space.