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Gamma Radiation: Definition, Uses & Equation

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Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

Gamma radiation or gamma rays are waves of the electromagnetic spectrum and a form of ionizing radiation. Learn more about the definition of gamma radiation, its equation, sources, and effects, including PET scans and killing cancer cells. Updated: 11/02/2021

What Is Gamma Radiation?

Human eyes are amazing detectors of electromagnetic radiation. They can see a lot. But there's a lot more that our eyes can't detect. A rainbow shows you all the colors of visible light that can be seen by our eyes. But beyond the red end of the spectrum there are radio waves, microwaves, and infrared radiation, and beyond the violet end there are x-rays, ultraviolet radiation, and gamma rays. The full electromagnetic spectrum is shown here:

The Electromagnetic Spectrum
The Electromagnetic Spectrum

Gamma radiation (otherwise known as gamma rays) is made up of waves that are just one part of the electromagnetic spectrum. They are high energy and can be dangerous, although contrary to the famous origin story, gamma rays won't turn you into the Hulk.

The name 'gamma rays' was coined by Ernest Rutherford. Previously, 'alpha rays' and 'beta rays' had been discovered through the study of radioactivity, named after the first two letters of the Greek alphabet. Paul Villard discovered gamma rays, but thought they were just another form of alpha or beta ray. Ernest Rutherford realized they were a new phenomenon and decided to continue the pattern, naming them gamma rays.

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  • 0:00 What Is Gamma Radiation?
  • 1:15 Sources of Gamma Rays
  • 2:10 Effects of Gamma Radiation
  • 2:30 Uses of Gamma Radiation
  • 3:17 Lesson Summary
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Sources of Gamma Rays

Gamma rays mainly come from two sources: radioactive materials and cosmic interactions. Radioactive materials are unstable and have a lot of excess energy. When they decay into simpler materials, they give off dangerous radiation of various types, one of which is gamma radiation.

When gamma rays are produced from radioactive materials, it is through a process called gamma decay. This is where jiggled-up radioactive atoms are able to release some of their high energy by emitting a gamma ray. The following equation describes that process:

Gamma Decay Equation

But gamma rays can also form in high energy cosmic interactions of charged particles in space, such as in active galactic nuclei at the center of galaxies. Most of these cosmic gamma rays are screened by Earth's atmosphere and don't make it far enough to be detected.

Gamma rays can also be produced after lightning strikes and randomly in the atmosphere during thunder storms.

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