(i) What characteristic property of nuclear force explains the constancy of binding energy per nucleon (BE/A) in the range of mass number ‘A’ lying `30 lt A lt 170`?
(ii) Show that the density of nucleus over a wide range of nuclei is constant-independent of mass number A.

Explanation

(i) Constancy of binding energy per nucleon in the range of mass number ‘A’ ranging from 30 to 170 can be explained on the basis of short ranged nature of nuclear force.
Inside a sufficiently large nucleon a particular nucleon is under the influence of only some of its neighbours which come within the range of the nuclear force. If a nucleon can have a maximum of p neighbours within the range of nuclear force, its binding energy would be proportional to p or the binding energy of the nucleon will be pk where k is a constant having the dimensions of energy.
Thus, it is clear that the binding energy per nucleon is a constant and equal to pk.