This is the thin lens equation, which is derived from ray diagram geometry.

这是薄透镜透镜方程，它是导数 从射线照相的几何形状。

Likewise, the thin lens equation is still applicable in most of our basic situations.

同样，薄透镜方程仍然 适用于我们的大多数基本情况。

For a diverging lens, the thin lens equation is still true, but the focal length is now a negative value.

对于间隔透镜，薄透镜方程仍然是 正确，但现在的焦距是 负值。

We draw this line because if we assume a thin lens, then we can draw a straight line through the center and disregard the slight offset that would occur due to refraction.

我们画这条线是因为如果我们假设镜片很薄，我们可以画一条穿过中心的直线，而忽略因折射而可能发生的轻微像差。