1. The problem statement, all variables and given/known data A 2 cm tall object is 20 cm to the left of a lens with a focal length of 10 cm. A second lens with a focal length of 15 cm is 30 cm to the right of the first lens. Calculate the image position and height. Compare with ray-tracing. 2. Relevant equations 1/f = 1/do + 1/di, m = -di/do and hi/ho; f: focal point, do: object distance, di: image distance, hi: image height, ho: object height. 3. The attempt at a solution 1/dia = 1/10 - 1/20, dia=20 cm; 1/dib = 1/15 - 1/(-dia+30), dib=-30 cm. (a denotes first lens, b second). And this is where I stumble. Looking in the back of the book, the correct answer seems to be: dib=30 cm, hib=6.0 cm. Doing the previous problems, the measurements are relative from the second lens, and after comparing the result with my ray diagram 30 cm, or -30 cm for that matter, is no where near my second image convergence point.