What is a beta particle?

A beta particle is specifically defined as a high-speed electron or positron that is emitted from a nucleus during the process of beta decay. In beta decay, a neutron in the nucleus of an atom is transformed into a proton, or vice versa, which results in the emission of the beta particle. When a neutron decays into a proton, an electron is emitted (this is referred to as a beta minus particle), while the positron is emitted when a proton transforms into a neutron (beta plus particle).

This understanding is crucial because it highlights the connection between beta particles and nuclear processes, pointing to their role in transforming one type of elementary particle into another, thus changing the identity of the atom itself (e.g., changing an element into another element).

Due to this established definition and behavior of beta particles, the answer correctly identifies the nature of a beta particle in the context of nuclear physics.