1. The problem statement, all variables and given/known data An object is in the focal length of a convex lens. As the object is moved from the focus towards the lens, what happens to the object? 2. Relevant equations 1/f=1/d0+1/di 3. The attempt at a solution I know how to solve this problem using ray diagrams, and the solution is: The image increases in size and moves farther from the lens I am trying to conclude this algebraically instead of just with a ray diagram. Just choosing numbers though, I let f=5 and do=4. Plugging this into the thin lens equation, I find that d0=-20, showing a virtual image on the same side of the lens as the object. However, then when I move the image closer and let f=5 and d0=3, the thin lens equation gives that d0=-7.5. Hence it seems to me that as the object is moving closer, it is still past the focal point, but moving closer to the lens as opposed to farther. Why is the numerical example leading to different results than the ray diagram? Thanks in advance!