Radioactivity: Definition, Types & Uses

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  • 0:04 What Is Radioactivity?
  • 1:19 Alpha Particles
  • 2:28 Beta Particles
  • 3:52 Gamma Rays
  • 5:55 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson, we'll be learning about the three types of radioactivity: alpha, beta and gamma radiation. By the end of the lesson, you'll be able to explain what makes these three types unique and how humans use them.

What Is Radioactivity?

In films, radioactivity is often portrayed as green slime leaking from barrels to produce three-eyed fish, or humans with superpowers. However, radioactivity isn't quite that dramatic, and it usually isn't green, either. Humans use radioactivity all the time, from medicine to food production.

Radioactivity, although it might sound scary, is simply elements losing different particles in their nucleus, releasing energy as they change. Every element has a characteristic amount of protons and neutrons, tiny particles inside an atom that make up their core, or nucleus. The amount of protons an element has gives it its identity, called the atomic number. During radioactivity, the atom loses some neutrons and/or protons, physically changing it into another element and emitting large amounts of energy. This process happens randomly in nature, but it can also be created by humans, such as inside a nuclear reactor.

There are different types of radioactivity depending on what particles or energy are released during the reaction. The three types are: alpha particles, beta particles, and gamma rays.

Alpha Particles

Think about building a block tower. With each block, there is a greater chance of the tower falling. It becomes more precarious, and even the slightest vibration is likely to send it to the floor. It turns out that atoms are quite similar to this. Atoms that have too many neutrons or protons tend to become unstable. This allows them to become radioactive.

In an effort to become more stable, the atom releases two protons and two neutrons, an alpha particle. Alpha particles are the largest products of radioactivity. Hence, they don't penetrate through many barriers like other types of radiation do, making them the least harmful to humans.

However, that doesn't mean humans can't find uses for them. One common use for alpha decay is in smoke detectors, which uses the radioactive element, americium. Thin sheets of americium are separated in your smoke detector. When plugged in, a small electric current runs through the plates creating ions in the air due to the energy released by the alpha particles, called ionization. If smoke gets into the smoke detector, it disrupts the current, stops the ionization and the alarm goes off.

Beta Particles

Beta particles are smaller than alpha particles and can penetrate further, up to the thickness of aluminum foil. During beta decay, the number of protons changes, either through gaining or losing protons. Beta particles can be used in manufacturing products, or in human medicine.

Imagine getting a diagnosis of thyroid cancer. Cancer can be difficult to get rid of, and there currently isn't a cure, although doctors can help you manage the disease. If surgery to remove the cancer isn't successful, your doctor might try radiation therapy. In this therapy, an isotope of iodine, iodine-131, is injected into the patient. The thyroid uses iodine to produce the thyroid hormone and is preferentially taken up by the thyroid. The beta particles, and some high energy gamma rays, are damaging to the thyroid, so they kill the cancer cells there.

Although pretty different from treating thyroid cancer, beta particles are also used to manufacture products like aluminum foil. Part of the usefulness of aluminum foil is that it is so thin and flexible. Imagine trying to wrap up leftovers with a thick, solid sheet of foil.

During manufacturing, beta particles are released near the aluminum foil. Beta particles just penetrate through aluminum. So scientists place a Geiger counter on the opposite side of the foil, which measures radiation. When the Geiger counter detects the radiation from the beta particles, the aluminum foil is thin enough.

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