Question

a compound microscope with objective of 1 cm focal length , eyepiece 2 cm focal length has a tube of length 20 cm. find the magnification if the image is formed at the near point.

Answer 1

$$\begin{gathered} \mathrm{Magnification}\mathrm{of}\mathrm{objective}: \\ {\mathrm{m}}_0=-\frac{\mathrm{L}}{{\mathrm{f}}_0} \\ \mathrm{Magnification}\mathrm{of}\mathrm{eyepiece}: \\ {\mathrm{M}}_{\mathrm{e}}=\frac{25}{{\mathrm{f}}_{\mathrm{e}}} \\ \mathrm{Total}\mathrm{magnification}: \\ \mathrm{M}={\mathrm{m}}_0{\mathrm{M}}_{\mathrm{e}} \\ =-\frac{25\mathrm{L}}{{\mathrm{f}}_0{\mathrm{f}}_{\mathrm{e}}} \\ =\frac{-25\times 20}{1\times 2} \\ =\mathbf{-}\mathbf{250} \end{gathered}$$