1. The problem statement, all variables and given/known data The barrel of a compound microscope is 15.9 cm in length. The specimen will be mounted 1.17 cm from the objective, and the eyepiece has a 5.00 cm focal length. Determine the focal length of the objective lens. 2. Relevant equations I am using the mirror equation. 3. The attempt at a solution 1/1.17 cm+1/s'=1/15.9 cm -1.26 cm adding 1.26 to 1.17=2.433 1/2.433+1/x=1/1.17 this gives me 2.25 cm I am so lost. Any guidance would be appreciated.