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Radiation & Radioactivity. In preparation for the Radioactivity iLab on iLabCentral.org Created by: Northwestern University, Office of STEM Education Partnerships

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Radiation & Radioactivity

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Radiation & Radioactivity

In preparation for the Radioactivity iLab

on iLabCentral.org

Created by: Northwestern University, Office of STEM Education Partnerships

Some information was provided by the United States Environmental Protection Agency, U.S. Dept. of Labor Occupational Safety & Health Administration, Radiation Answers, and the Non-Destructive Testing Resource Center.


  • Radiation is the emission of energy from a source that travels in the form of either:

    1) waves

    2) high-speed particles

  • As the root word “radiate” implies, when energy travels via radiation, it spreads out in all directions from a central point.

  • Many types of energy radiate through space including light and heat.

What is radiation?


Yes there are different types of radiation, which can generally broken down into two categorizations:

Electromagnetic vs. Particle radiation

Ionizing vs. Non-ionizing radiation

Are there different types of radiation?


  • Radiation in the form of waves is called electromagnetic radiation.

  • Electromagnetic radiation is used in microwave ovens, TVs, cell phones, power lines, and even sunshine.

  • These types of radiation have different wavelengths & frequencies along the electromagnetic spectrum (right).

Electromagnetic Radiation


  • Radiation in the form of high-speed particlesis called particle radiation.

  • Particle radiation happens when an unstable nucleus releases energy in the form of fast-moving sub-atomic particles, in order to become more stable.

  • The main examples of particle radiation are alpha and betaparticles, which are released from certain radioactive materials as they decay over time.

Particle Radiation


  • Ionizing radiationhas enough energy to break chemical bonds in molecules, or remove tightly bound electrons from atoms, which creates charged molecules or atoms (ions).

    • The ionization releases energy that is absorbed by material surrounding the ionized atom.

    • Ionizing radiation can be both electromagnetic and particle radiation.

    • Exposure to this type of radiation is dangerous to humans, because it can cause damage to living tissue.

  • Non-ionizing radiation has enough energy to move atoms in a molecule, but not enough energy to remove electrons.

    • Non-ionizing radiation is not as harmful to people as ionizing radiation.

  • Ionizing vs. Non-Ionizing Radiation


    Ionizing vs. Non-Ionizing Radiation

    Credit: Canadian Nuclear Association


    • Radioactivity is the spontaneous emission of energy from an unstable nucleus of an atom by radiation, in the form of particles or rays.

    • This process is also known as radioactive decay, in which an unstable (radioactive) nucleus emits ionizing radiation and becomes more stable.

    • Examples of radioactive materials are strontium-90, plutonium-239, carbon-14, uranium-235, and iodine-131.

    What is radioactivity, or radioactive decay?


    • Alpha () particles

      • Made up of two protons and two neutrons bound together

      • They move slowly and can be stopped by a sheet of paper or human skin

    • Beta () particles

      • Made up of electrons

      • They move faster than alpha but lose their energy when they collide with other atom

      • Some beta particles can be stopped by human skin, but if they are ingested, the particles can be absorbed into the bones and cause damage

    • Gamma () rays

      • High-frequency photons with no charge

      • Can penetrate paper and aluminum, but are stopped by a thick layer of lead or concrete (think of wearing lead vests when getting x-rays)

      • If a person is exposed to gamma rays, severe damage can be caused to their internal organs

    What types of radiation are emitted during radioactive decay?

    Credit: Wikipedia


    • Radioactivity is measured by a Geiger counter, which measures ionizing radiation by counting the number of particles or rays (photons) it detects.

    • Geiger counters usually consist of three parts:

      • 1) Geiger-Mueller tube – a gas-filled tube whose gas ionizes when charged particles or photons from radioactive material pass through the gas

      • 2) Visual readout – a meter that keeps track of the number of radioactive particles or photons being detected by the Geiger counter

      • 3) Audio readout – a meter that makes one “click” sound for each radioactive particle or photon detected by the Geiger counter

    • Hear what a Geiger counter sounds like:

      http://www.geigercounters.com/Geiger.wav

    How is radioactivity measured?

    Credit: ThinkQuest


    • The lab equipment consists of:

      • 1) A Geiger counter

      • 2) A radioactive strontium-90 sample

    • You can set:

      • 1) The distances in mm from the strontium-90 source, at which radiation can be measured (in units of “particle counts”)

      • 2) The measurement time in seconds that each measurement of particle counts will last

      • 3) The number of trials that will be conducted

    • In this lab, you can study how the intensity of radiation changes over distance.

    The Radioactivity iLab


    • Strontium (Sr) is a silvery metal, and turns yellow quickly when exposed to air.

    • Strontium-90 emits beta particlesas it decays. It is found in nature and often in waste from nuclear reactors. It is considered one of the more hazardous components of nuclear wastes.

    • Strontium-90 has a half-life of 29.1 years, meaning it takes 29.1 years for half of a sample of strontium-90 to decay by emitting radioactive particles.

    Credit: eHow

    What is strontium-90?

    Credit: Ricarose Roque


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