1. The problem statement, all variables and given/known data A lens of focal length 0.8m is 1.0 m to the left of a mirror of focal length -0.500m. An object is placed 1.00 m to the left of the lens. Light goes through the lens, bounces from the mirror, and goes through the lens again, this time from the right. 2. Relevant equations 1/f=1/di+1/do 3. The attempt at a solution (THIS IS FROM THE OFFICIAL SOLUTION MANUAL, I AM CONFUSED ON PART OF THE ANSWER TOWARDS THE END) 1/di1=1/f1-1/do1 1/di1=1/0.8-1/1 di1=4.0 m This image is 3 meters behind the mirror, so do2 for the mirror is -3.0 m. 1/di2=1/f2-1/do2 1/-0.5-1/-3=1/di2 di2= -0.6 m This image is behind the mirror. THIS IS WHERE I GET CONFUSED: di3 (for the lens)=1+0.6m=1.6m 1/di2=1/f1-1/do3=1/0.8-1/1.6 di3=1.6m In this instance, why is di3 postive 1.6 m instead of negative 1.6 meters? The "object" is to the right of the lens, so shouldn't di3 be negative?