Radioactivity and Particles: Ionising Radiation

Radioactivity and Particles: Ionising Radiation

-Ionising radiation refers to any form of radiation that has sufficient energy to remove tightly bound electrons from atoms, thus converting atoms into charged ions.

-Three common types are alpha particles (α), beta particles (β), and gamma rays (γ).

-Alpha particles are helium nuclei comprised of two protons and two neutrons. They have a charge of +2 and can ionise atoms over a short distance - a few centimetres in air. They can be stopped by a sheet of paper.

-Beta particles are high-speed electrons or positrons (with a charge of -1 or +1) ejected from the nucleus of an atom. They have a higher range than alpha particles - a few metres in air. They can be stopped by an aluminium sheet.

-Gamma rays are electromagnetic waves, similar to X-rays. Unlike alpha and beta particles, gamma rays have no mass or charge. They can travel several hundred metres in air and require thick layers of lead or concrete for shielding.

-Ionising radiation can cause harm to living organisms because ions that are produced by radiation can damage biological molecules. This may result in mutation, radiation sickness, or cancer.

-Radiation is measured in units called becquerels (Bq), where one Bq is one decay per second. The effects of exposure are measured in sieverts (Sv) or in millisieverts (mSv), which are one thousandth of a sievert.

-Different materials have different half-lives, which is the time it takes for half of the radioactive atoms in a sample to decay. This term is commonly used to measure the rate of decay.

-Background radiation refers to the continuous and omnipresent radiation in our environment. It has numerous sources including cosmic rays from outer space, naturally radioactive materials such as uranium in the soil, and even man-made sources like x-rays and nuclear power plants.

-Radiation can prove beneficial in healthcare, specifically in cancer treatment (radiotherapy) and medical imaging (radioactive tracers).

UNDERSTAND: The hazards from ionising radiation: Alpha Particles pose the greatest external threat when inhaled or ingested. Gamma rays carry the highest risk as external sources due to their high penetrating power.

  • Ionising radiation can be detected and measured using a Geiger-Müller tube and counter.

-Unlike alpha and beta particles, gamma rays have a high penetrating power, due to their wave nature. This makes them useful in many applications but also particularly dangerous.