What Are Beta Rays?

Beta rays refer to the emission of beta particles (symbolized by the lowercase Greek character of the same name.) Beta particles are simply electrons that have been accelerated to a highly energetic state. Along with gamma rays and alpha particles, beta rays are classified as ionizing radiation. Ionizing radiation is dangerous to living matter (including people), and so it is important to understand its causes to know how to avoid potential health concerns.

Properties of Beta Rays

• Beta rays are streams of highly energetic electrons, or beta particles, emitted by unstable isotopes in a process called "beta decay." Like all electrons, beta particles have a charge of -1 and a mass of 1/1823th of an atomic unit. Beta particles typically travel only a few inches before bonding with a molecule, at which point they revert to simply being electrons. Beta rays generally are not energetic enough to pass through solid material.

The Cause of Beta Rays

• Beta decay is the transformation by which an atom lowers its total energy by transforming a neutron into a an electron-proton pair. The addition of a proton changes the chemical element of the atom, but the electron is ejected at high energy levels. This happens if there is an unstable ratio of neutrons to protons within an atomic nucleus. Because neutrons require the forces of the atomic nucleus to stay whole, free-floating neutrons have a half-life of only 10 minutes.

Sources of Beta Rays

• Some medical imaging techniques create an image from beta rays emitted by an unstable isotope injected into the body.

  Most beta radiation on earth takes place in heavy atomic nuclei where the number of neutrons exceeds the number of protons in an unstable ratio. Though usually associated with rare earth elements, beta decay also occurs in isotopes of light elements and can be harnessed for beneficial uses. For example, carbon dating relies on the predictable beta decay of C-14. Beta radiation from strontium-90 is used in cancer treatment and as a medical imaging tracer.

Health Concerns of Beta Rays

• Like all ionizing radiation, beta rays can damage tissue by altering the molecular bonds in cells. While some ionizing radiation comes from natural sources, prolonged or intensified exposure is a serious health risk. Topical exposure to beta rays can result in redness or burning of the skin, and inhaling particles emitting beta rays can cause internal damage. Because free-floating neutrons have a beta decay half-life of 10 minutes, neutron beams are a dangerous source of beta radiation.