Nuclear physics is a branch of physics that deals with protons, neutrons, nucleons, and the interactions between them.
The study of nuclear decay, nuclear fusion, nuclear fission come under this branch.
Ernst Rutherford is called the father of physics.
He was a New Zealand physicist who discovered the concept of radioactive half-life, the radioactive element Radon, and the particle that exists in the nucleus of an atom, the proton.
He proved with his colleague Thomas Royds that the particle emitted in alpha radiation is the nuclei of the Helium atom.
He proposed the Rutherford model of atom.
He also theorized the existence of neutron which was later discovered by James Chadwick.