1.4 Types of Ionizing Radiation

Alpha Particles (\(\alpha\))

An alpha particle is a heavy, positively charged particle composed of two protons and two neutrons (identical to a helium nucleus). Due to its large mass and charge, it interacts strongly with matter, losing energy quickly. This gives it a very low penetrating power; a sheet of paper or the outer layer of skin can stop it. However, if an alpha-emitting material is ingested or inhaled, the high energy deposition in a small area makes it a significant internal hazard.

Beta Particles (\(\beta\))

A beta particle is a small, fast-moving particle, either an electron (\(\beta^-\)) or a positron (\(\beta^+\)). It has a much smaller mass and charge than an alpha particle, allowing it to penetrate materials more deeply. Beta particles can be stopped by a thin sheet of plastic or aluminum, but can penetrate the skin. A beta particle is created during radioactive decay when a neutron converts into a proton (or vice versa), and is then ejected from the nucleus.

Gamma Rays (\(\gamma\)) and X-rays

Gamma rays and X-rays are a form of electromagnetic radiation, just like visible light, but with much higher energy. They have no mass and no charge, giving them very high penetrating power. They are typically stopped by dense materials like lead or concrete.

• Gamma Rays: Originate from the nucleus of an atom during a decay process.
• X-rays: Originate from the electron shells of an atom or from the acceleration of electrons, such as in an X-ray tube.

Neutrons (\(n^0\))

A neutron is a neutral particle with no electric charge. Because it has no charge, it does not interact electrically with the electrons or nuclei of atoms. This allows it to travel a long distance and penetrate materials very effectively. Neutrons interact with matter primarily through nuclear reactions, scattering, or absorption. They are an important type of radiation in nuclear reactors and high-energy physics.