(a) For the telescope described what is the separation between the objective lens and eye piece ?
(b) If this telescope is used to view a `100 m` tall tower `3 km` away, what is the height of the image of the tower formed by the objective lens ?
(c ) What is the height of the final image of the tower if it is formed at 25 cm` ?

Explanation

(a) `f_(O)+f_(e)=145cm`
(b) Angled subtended by the tower `=(100//3000)=(1//30)`rad
Angled subtended by the image produced by the objective `=(h)/(f_(O))=(h)/(140)`
Equating the two, `h=4.7cm`.
(c) Magnification (magnitude) of the eye-piece = 6. Height of the final image (magnitude) = 28 cm.