nuclear physics Branch of physics concerned with the structure and properties of the atomic nucleus. The principal means of investigating the nucleus is the scattering experiment, carried out in particle accelerators, in which a nucleus is bombarded with a beam of high-energy elementary particles, and the resultant particles analyzed. Study of the nucleus has led to an understanding of the processes occurring inside stars and has enabled the building of nuclear reactors.

nu·cle·ar phys·ics • pl. n. [treated as sing.] the physics of atomic nuclei and their interactions, esp. in the generation of nuclear energy.