Summary Thus Far
Starting with an object a finite distance to the left of a convex lens that is strong enough to form an image to the right of the lens (that is, with a focal length f shorter than the object distance), there are 2 ways to move the image to the left (closer to the lens): by moving the object to the LEFT or by adding an additional convex lens to the lens system. Similarly, there are 2 ways to move the image to the right (farther from the lens): by moving the object to the RIGHT (so long as it remains farther from the lens than the focal length) or by adding a concave lens to the system.
Figure I-10 Formation of a virtual image of an object infinitely far away to the left of the lens by a concave lens. The focal point is to the left of the lens; the focal length is a negative number, and the power of the lens P = 1/f is likewise negative.
Excerpted from BCSC 2020-2021 series : Section 3 - Clinical Optics. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.