Explanation

(c) When atoms of an element are bombarded by neutrons, the atomic nuclei are (artificially) disintegrated and emit lighter particle ($eg$. $\alpha - particle,\ \beta - particle$,proton etc.). Sometimes a neutron is observed by the nucleus which is converted into its heavier isotope and energy is emitted in the form of $\gamma$-photons. This process in which heavy nucleus is broken into two nearly equal fragments is called nuclear fission.