Particles emitted from a radioactive material are observed to be deflected in a magnetic field. These particles may be

Radioactive materials spontaneously emit three primary types of radiation: alpha particles, beta particles, and gamma rays [c1, t1]. Alpha particles are positively charged helium nuclei consisting of two protons and two neutrons [t5]. Beta particles are fast-moving electrons and are negatively charged [t2]. According to the Lorentz force principle, charged particles moving through a magnetic field experience a force that causes deflection [t1, t3]. Since both alpha particles (protons) and beta particles (electrons) carry electric charges, they are deflected in opposite directions within a magnetic field [t2, t4, t8]. In contrast, gamma rays are uncharged electromagnetic waves and remain undeflected [t1, t3]. Neutrons, being electrically neutral, also do not experience deflection in a magnetic field. Therefore, the particles observed to be deflected may be electrons, protons, or both [c1, t1].

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > Radioactivity: > p. 82
2. [2] https://kids.britannica.com/students/assembly/view/171590