Question

Write down the magnification formula for a lens in terms of object distance and image distance. How does this magnification formula for a lens differ from the corresponding formula for a mirror?

Answer 1

Magnification formula for a lens is given by:
$$\begin{gathered} \mathrm{m}=\frac{\mathrm{v}}{\mathrm{u}} \\ \mathrm{Magnification}\mathrm{formula}\mathrm{for}\mathrm{a}\mathrm{mirror}\mathrm{is}\mathrm{given}\mathrm{by}: \\ \mathrm{m}=-\frac{\mathrm{v}}{\mathrm{u}} \\ \mathrm{For}\mathrm{both}\mathrm{the}\mathrm{formulas}, \\ \mathrm{m}=\mathrm{Magnification} \\ \mathrm{v}=\mathrm{Image}\mathrm{distance} \\ \mathrm{u}=\mathrm{Object}\mathrm{distance} \end{gathered}$$

There is a difference of negative sign between the lens formula and the mirror formula. In mirror magnification formula, negative sign is present, whereas in lens magnification formula, this negative sign is not present.