Background Radiation (Edexcel GCSE Physics): Revision Note

Background Radiation

• It is important to remember that radiation is a natural phenomenon

• Radioactive elements have always existed on Earth and in outer space

  • However, human activity has added to the amount of radiation that humans are exposed to on Earth

• Background radiation is defined as:

  The radiation that exists around us all the time

• There are two types of background radiation:

  • Natural sources

  • Man-made sources

Background radiation is the radiation that is present all around in the environment. Radon gas is given off from some types of rock

• Every second of the day there is some radiation emanating from natural sources such as:

  • Rocks

  • Cosmic rays from space

  • Foods

Origins of Background Radiation

• Background radiation can come from natural sources on Earth or space and man-made sources

Natural Sources

• Radon gas from rocks and soil

  • Heavy radioactive elements, such as uranium and thorium, occur naturally in rocks in the ground

  • Uranium decays into radon gas, which is an alpha emitter

  • This is particularly dangerous if inhaled into the lungs in large quantities

• Cosmic rays from space

  • The sun emits an enormous number of protons every second

  • Some of these enter the Earth’s atmosphere at high speeds

  • When they collide with molecules in the air, this leads to the production of gamma radiation

  • Other sources of cosmic rays are supernovae and other high energy cosmic events

• Carbon-14 in biological material

  • All organic matter contains a tiny amount of carbon-14

  • Living plants and animals constantly replace the supply of carbon in their systems hence the amount of carbon-14 in the system stays almost constant

• Radioactive material in food and drink

  • Naturally occurring radioactive elements can get into food and water since they are in contact with rocks and soil containing these elements

  • Some foods contain higher amounts such as potassium-40 in bananas

  • However, the amount of radioactive material is minuscule and is not a cause for concern

Man-Made Sources

• Medical sources

  • In medicine, radiation is utilised all the time

  • Uses include X-rays, CT scans, radioactive tracers, and radiation therapy

• Nuclear waste

  • While nuclear waste itself does not contribute much to background radiation, it can be dangerous for the people handling it

• Nuclear fallout from nuclear weapons

  • Fallout is the residue radioactive material that is thrown into the air after a nuclear explosion, such as the bomb that exploded at Hiroshima

  • While the amount of fallout in the environment is presently very low, it would increase significantly in areas where nuclear weapons are tested

• Nuclear accidents

  • Accidents such as that in Chernobyl contributed a large dose of radiation into the environment

  • While these accidents are now extremely rare, they can be catastrophic and render areas devastated for centuries

Corrected Count Rate

• Background radiation must be accounted for when taking readings in a laboratory

• This can be done by taking readings with no radioactive source present and then subtracting this from readings with the source present

  • This is known as the corrected count rate