A convex mirror of focal length magnitude 20 cm forms an erect image with magnification +1/3. What is the object distance?
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A convex mirror of focal length magnitude 20 cm forms an erect image with magnification +1/3. What is the object distance?

G1 Physics · Accepted Answer

For a convex mirror, m=−v/u=+1/3, so |v|=|u|/3. Using the Cartesian sign convention, f=+20, u<0 and v>0. Substitution gives |u|=40 cm.