Alpha, Beta, and Gamma Radiation - SS2 Physics Lesson Note

Alpha, beta, and gamma radiation are three types of ionising radiation emitted during radioactive decay. Each type has different properties and interactions with matter.

Alpha Radiation:

Alpha radiation consists of alpha particles, which are helium nuclei composed of two protons and two neutrons. Alpha particles have a positive charge and are relatively large and heavy. Due to their size and charge, alpha particles have low penetrating power and are easily stopped by a few centimetres of air or a sheet of paper. However, alpha particles can be highly damaging if they are inhaled or ingested because they can cause ionisation and damage living tissue. Examples of radioactive isotopes that emit alpha particles include uranium-238, radium-226, and radon-222.

Beta Radiation:

Beta radiation involves the emission of beta particles, which can be either beta-minus particles (electrons) or beta-plus particles (positrons). Beta-minus decay occurs when a neutron in the nucleus converts into a proton, emitting an electron and an antineutrino. This process increases the atomic number of the nucleus. Beta-plus decay involves the conversion of a proton into a neutron, emitting a positron and a neutrino. This process decreases the atomic number of the nucleus. Beta particles have a negative charge and are smaller and lighter than alpha particles. They have moderate penetrating power and can pass through several millimetres of aluminium. However, beta particles can still cause damage to living tissue if they come into direct contact with it. Examples of isotopes that emit beta particles include carbon-14, iodine-131, and strontium-90.

Gamma Radiation:

Gamma radiation is electromagnetic radiation emitted from the nucleus during radioactive decay. Gamma rays are highly energetic photons with no mass or charge. Gamma radiation has the highest penetrating power among the three types and can travel long distances through air, paper, and even thick materials like concrete and lead. It requires several centimetres of lead or several metres of concrete to significantly reduce gamma ray intensity. Gamma rays are often emitted together with alpha or beta particles to bring the nucleus to a lower energy state. Gamma radiation can cause ionisation and damage living tissue, similar to alpha and beta radiation. Examples of isotopes that emit gamma radiation include cobalt-60, cesium-137, and technetium-99m.

In summary, alpha, beta, and gamma radiation are three types of ionising radiation emitted during radioactive decay. Alpha particles are helium nuclei with low penetrating power but can be highly damaging if inhaled or ingested. Beta particles are electrons or positrons with moderate penetrating power. Gamma rays are high-energy photons with the highest penetrating power. Understanding the properties and interactions of these types of radiation is crucial for radiation safety, medical applications, and various fields of scientific research.