Gamma ray

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Gamma rays (often denoted by the Greek letter gamma, γ) are an energetic form of electromagnetic radiation produced by radioactive decay or other nuclear or subatomic processes such as electron-positron annihilation.

Gamma rays form the highest-energy end of the electromagnetic spectrum. Gamma rays are a form of ionizing radiation; they are more penetrating than either alpha or beta radiation (neither of which is electromagnetic radiation), but less ionizing. Gamma sources are used for a range of applications in both medicine and industry.

 

Interaction with matter

Gamma rays are often produced alongside other forms of radiation such as alpha or beta.
When a nucleus emits an α or β particle, the daughter nucleus is sometimes left in an excited state. It can then jump down to a lower level by emitting a gamma ray in much the same way that an atomic electron can jump to a lower level by emitting ultraviolet radiation.

Gamma rays have made them useful in the sterilization of medical equipment by killing bacteria.

They are also used to kill bacteria and insects in foodstuffs, particularly meat and vegetables, to maintain freshness.