(a) The separation between the objective lens and the eyepiece
= f0 + fe = 140 + 5 = 145 cm.
(b) height of the tower = 100 m; distance = 3 km = 3000 m.
Angle subtended by the tower = 100/3000 = 1/30 rad
Angle subtended by the image produced by the objective
= h/f0 = h/140
∴ h/140 = 1/30
∴ h = 140/30 = 4.7cm
(c) Magnification produced by eyepiece
= (1 + d/fe) = (1 + 25/5) = 6
∴ Height of final image = 14/3 x 6 = 28 cm.