posted by lily on .
A cosmetic mirror is 50cm from your face and the magnified image of your face is upright. You are told that the focal length of the mirror is 45cm. Explain why this focal length is not possible.
I understand that the image would be magnified and upright...that's about it
In this case, the image distance, di, is negative and |di| > do for magnification > 1
1/do + 1/di = 1/do -|1/di| = 1/f
1/50 -1/|di| = 1/45
This is not possible. The 1/|di| term must be positive