Radiation can refer to two different things in physics: electromagnetic radiation and particulate radiation.
Electromagnetic Radiation: Electromagnetic radiation refers to the propagation of energy through space in the form of oscillating electric and magnetic fields. It includes a broad range of phenomena, such as radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays. Electromagnetic radiation behaves both as waves and particles called photons. In this context, radiation is not a particle itself, but rather a phenomenon that can be described by both wave and particle properties.
Particulate Radiation: Particulate radiation consists of high-energy particles that are emitted from atomic nuclei or subatomic processes. These particles can include alpha particles (helium nuclei), beta particles (electrons or positrons), neutrons, and protons. Particulate radiation differs from electromagnetic radiation in that it consists of discrete particles, rather than waves.
In summary, while electromagnetic radiation can be described as both waves and particles (photons), particulate radiation consists of discrete particles.