The focal length of the objective lens of a telescope is 30 cm and that of its eye lens is 3 cm. It is focused on a scale at a distance 2 m from it. The distance of objective lens from eye lens to see the clear image is

Step-by-step solution

for a telescope, f _ o =30 ~cm , f _ e =3 ~cm , u _ o =-200 ~cm For objective lens, aligned & 1 f_o = 1 v₀ - 1 u_o & 1 30 = 1 v_o - 1 -200 1 v₀ = 1 30 - 1 200 aligned v _ o =35.3 ~cm To see clear image, it should be formed at infinity. Distance between objective and eye lens is L = v _ o + f _ e =35.3+3=38.3 ~cm