d) Why must both the objective and the eyepiece of a compound microscope have short focal lengths ?

Explanation

d) Angular magnification of eye piece is `(1+(d)/(f_(e)))`. This increases as `f_(e)` decreases. Further, magnification if objective lens is `(upsilon)/(u)`. As object lies close to focus of objective lens `u~~f_(0)`. To increase this magnification `(upsilon//f_(0)),f_(0)` should be smaller.