1. The problem statement, all variables and given/known data A science museum has created a huge concave mirror with a focal length of 5 m, and mounted it so that it covers the entire wall at one end of a long hallway. If you stand on a center line painted down the middle of the hallway, you're on the mirror's principal axis. You and a friend are standing on the center line, you're 8 m from the mirror, and your friend is 20 m from it. Can both you and your friend see the image of you created by the mirror? Explain. 2. Relevant equations 1/f-1/do = 1/di 3. The attempt at a solution I will be standing to close to the mirror to see myself, my friend can see me and himself in the mirror though. f is the focal length. (5m) do: will be the distance between the mirror and me. di: is the actual image from the mirror. so 1/f = 1/di + 1/do (whats the name of this equation?) solve for the image distance, di 1/f-1/do = 1/di (f*do)/(do-f) = di ..5m*8m/(8-5) = 13.33333333_ m. 13.3 repeating meters is farther away than i'm standing, but definately closer than what my friend is standing of 20 meters. So he can see me and himself in the mirror. If he can see me, than he should be able to see himself. Is there a way to prove this without actually calculating his distance out using the formula above?