Question -
Answer -
Focal length of the objective lens, fo = 140 cm
Focal length of the eyepiece, fe = 5 cm
(a) In normal adjustment, the separation between theobjective lens and the eyepiece 
(b) Height of the tower, h1 = 100 m
Distance of the tower (object) from thetelescope, u = 3 km = 3000 m
The angle subtended by thetower at the telescope is given as:
The angle subtended by theimage produced by the objective lens is given as:
Where,
h2 = Height of theimage of the tower formed by the objective lens
Therefore, the objectivelens forms a 4.7 cm tall image of the tower.
(c) Image is formed at adistance, d = 25 cm
The magnification of theeyepiece is given by the relation:
Height of the final image
Hence,the height of the final image of the tower is 28.2 cm.