Characteristics of Gamma Rays / Radiation

Key features of gamma rays are summarized in the following few points:

• Gamma rays are high-energy photons (about 10 000 times as much energy as the visible photons),
• The same photons as the photons forming the visible range of the electromagnetic spectrum – light.
• Photons (gamma rays and X-rays) can ionize atoms directly (despite they are electrically neutral) through the Photoelectric effect and the Compton effect, but secondary (indirect) ionization is much more significant.
• Gamma rays ionize matter primarily via indirect ionization.
• Although many possible interactions are known, there are three key interaction mechanisms with the matter.
  • Photoelectric effect
  • Compton scattering
  • Pair production
• Gamma rays travel at the speed of light, and they can travel thousands of meters in the air before spending their energy.
• Since gamma radiation is very penetrating, it must be shielded by very dense materials, such as lead or uranium.
• The distinction between X-rays and gamma rays is not so simple and has changed in recent decades.  According to the currently valid definition, X-rays are emitted by electrons outside the nucleus, while the nucleus emits gamma rays.
• Gamma rays frequently accompany the emission of alpha and beta radiation.

Image: The relative importance of various processes of gamma radiation interactions with matter.

Basic Principles of Shielding of Gamma Rays

See also: Shielding of Gamma Rays