Reference :

  • What is Gamma Ray
  • Gamma radiation, also known as gamma rays, and denoted by the Greek letter γ, refers to electromagnetic radiation of extremely high frequency and therefore high energy per photon.Wikipedia 

    Related topics

  • Very energetic gamma rays, with photon energies over ~30 GeV, can also be detected by ground based experiments. Wikipedia 
    In astronomy, higher energy gamma and X-rays are defined by energy, since the processes which produce them may be uncertain and photonenergy, not origin, determines the required astronomical detectors needed. Wikipedia 
    Gamma rays (gamma photons) are emitted from the nucleus of some unstable (radioactive) atoms. 

  • Is it safe to eat foods labeled "irradiated"?