Where should an object be placed in front of a convex lens so as to use it as a simple microscope?

15 How does an eye focus the objects lying at various distances? 16 When is a person said to have developed cataract in his eye? How is the vision of a person having cataract restored? 18 If we need magnification of 375 from a microscope of tube length 15 cm and objective of focal length 0.5 cm, what focal length of eye-piece should we use? 19 If focal length of the objective and eye-piece of a telescope are 10 cm and 4 cm respectively, what will be its magnifying power in
(i) normal adjustments,
(ii) adjustment where image of distance object is formed at D? Given D = 25 cm.