1. The problem statement, all variables and given/known data A 2.0-cm-diameter spider is 1.80 m from a wall. A. Determine the focal length of a lens that will make a half-size image of the spider on the wall. B. Determine the position (measured from the wall) of a lens that will make a half-size image of the spider on the wall. 2. Relevant equations (1/p) + (1/q) = (1/f) m = (-q/p) 3. The attempt at a solution I couldn't figure out where to start. I understand that the magnification should be (-.05) but then I can't use that equation because I don't know the original focal length. Would 1.80 m be the image distance? I wish the problem would have provided more information!