Question

Which shows the correct magnification equation?

StartFraction h Subscript I Baseline over h Subscript o Baseline EndFraction equals negative StartFraction d Subscript I Baseline over d Subscript o Baseline EndFraction.
StartFraction h Subscript I Baseline over h Subscript o Baseline EndFraction equals StartFraction d Subscript I Baseline over d Subscript o Baseline EndFraction.
StartFraction d Subscript I Baseline over d Subscript o Baseline EndFraction equals negative StartFraction h Subscript I Baseline over d Subscript o Baseline EndFraction.
StartFraction d Subscript I Baseline over d Subscript o Baseline EndFraction equals StartFraction h Subscript I Baseline over d Subscript o Baseline EndFraction.

Answer 1

The first option is correct:

h_I / h_O = − d_I / d_O.

This comes from similar triangles for a thin lens or mirror. The negative sign indicates that a real image is inverted relative to the object (so h_I and h_O have opposite signs).