JEE Main & Advanced Physics Nuclear Physics And Radioactivity Nuclear Force

Forces that keep the nucleons bound in the nucleus are called nuclear forces.

(1) Nuclear forces are short range forces. These do not exist at large distances greater than \[{{10}^{-15}}\,m\].

(2) Nuclear forces are the strongest forces in nature.

(3) These are attractive force and causes stability of the nucleus.

(4) These forces are charge independent.

(5) Nuclear forces are non-central force.

(6) Nuclear forces are exchange forces : According to scientist Yukawa the nuclear force between the two nucleons is the result of the exchange of particles called mesons between the nucleons.

\[\pi -\]mesons are of three types - Positive \[\pi \]meson \[({{\pi }^{+}})\], negative \[\pi \] meson \[({{\pi }^{-}})\], neutral \[\pi \] meson \[({{\pi }^{0}})\]

The force between neutron and proton is due to exchange of charged meson between them i.e.

\[p\to {{\pi }^{+}}+n,\,\,\,\,\,\,n\to p+{{\pi }^{-}}\]

The forces between a pair of neutrons or a pair of protons are the result of the exchange of neutral meson \[({{\pi }^{0}})\] between them i.e.

\[p\to p'+{{\pi }^{0}}\]   and    \[n\to n'+{{\pi }^{0}}\]

Thus exchange of p meson between nucleons keeps the nucleons bound together. It is responsible for the nuclear forces.

Dog-Bone analogy

The above interactions can be explained with the dog bone analogy according to which we consider the two interacting nucleons to be two dogs having a common bone clenched in between their teeth very firmly. Each one of these dogs wants to take the bone and hence they cannot be separated easily. They seem to be bound to each other with a strong attractive force (which is the bone) though the dogs themselves are strong enemies. The meson plays the same role of the common bone in between two nucleons.