Question

compound microscope consists of two convex lenses of focal length 2 cm and 5 cm. When an object is kept at a distance of 2.1 cm from the objective, a virtual and magnified image is fonned 25 cm from the eye piece.  Calculate the magnifying power of the microscope.

Answer 1

For objective lens (L₀ )      u₀=-2.1cm

                                          f₀ = 2 cm

                                        `1/(f_0)=1/(v_0) -1/(u_0)`

⇒                                       `1/2 =  1/(v_0)  +1/2.1`

⇒                                   `1/(v_0) = 1/2 - 1/(2.1) = (2.1-2)/(4.2) = 1/42` cm

                                           v₀ = 42 cm 

                    Magnifying ower = `(v_0)/(u_0) (1+D/(f_e))`;

[∵ Magnified image is formed 25 cm i.e., least distance ]

                Magnifying power = `42/(-2.1)(1+25/5)=-45/(2.1) xx6`

                Magnifying power = -120

negative sign shows the final image is inverted