1. The problem statement, all variables and given/known data A lens is made out of glass with a reflective index of 1.7, with a focal length of 20cm. An object at infinity will be in focus at a distance of ___________? a.10cm b.40cm c.50cm d.88cm e.20cm I have no idea how to approach this. I've tried to apply the thin lens equation, but it doesn't account for reflective index nor infinity. Help would be appreciated.