When viewing through a compound microscope our eyes should be positioned not on the eye piece, but a short distance away from it for best viewing , why ? How much should be the short distance between the eye and the eyepiece ?

Question

$\begin{array}{1 1} \text{The exact location of the eye ring depends upon the separation between the objective and eyepiece } \\ \text{It also depends on the focal length of the eyepiece } \\ \text{Ideal position for our eyes for viewing is this eye ring only } \\ \text{all of the above} \end{array} $