Draw a plot of the binding energy per nucleon as a function of mass number for a large number of nuclei, `2le Ale 240`. How do you explain the constancy of binding energy per nucleon in the range `30ltA lt170` using the property that nuclear force is short-ranged ?

Explanation

A plot of binding energy per nucleon as a function of mass number has been shown in Fig. 13.04.
The constancy of the binding energy per nucleon in the range `30 lt A lt 170` is a consequence of the fact that the nuclear force is short ranged one. A particular nucleon will be under the influence of only some of the neighbouring nucleons 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 is equal to pk where k is a constant. If we increase mass number A, by adding more nucleons, they will not change the binding energy of a nucleon inside.
Thus, binding energy per nucleon is a constant and is approximately equal to pk.