The Mirror Formula relates object distance ($u$), image distance ($v$), and focal length ($f$): $\frac{1}{f}=\frac{1}{v}+\frac{1}{u}$

• Sign Convention (Cartesian):
  • Source is on the left.
  • Distances in the direction of incident light are positive.
  • For a concave mirror, $f$ is negative.
  • For a convex mirror, $f$ is positive.