ABSTRACT
The concept of photon was introduced by Einstein to explain a newly discovered phenomenon called photoelectric effect, which could not be interpreted by classical theory of electromagnetic waves. Nuclear processes can be described by assuming that atomic nuclei are made up of protons and neutrons. The model for description of nuclear forces is similar to the model of electrical force. The atomic nucleus is a system of nucleons whose binding depends on the strong nuclear attractive force, and a hundred times weaker repulsive electric force acting between protons. A nuclear decay is a spontaneous process, which can occur only if energy is released, and the nucleus passes from a higher energy level to a lower one. The excited nuclear state can be obtained after the emission of a beta or alpha-particle, and in the nuclear reactions. The unstable nuclides are obtained by bombarding the stable nuclides with beams of particles which are produced either in accelerators or in nuclear reactors.
