AQA GCSE Physics

Revision Notes

4.3.1 Background Radiation

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

  • 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 Chart, downloadable AS & A Level Physics revision notes

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
  • Man-made sources of radiation increase the background radiation levels, examples include:
    • Fallout from nuclear weapons testing and nuclear accidents
    • Exposure from medical testing

Worked Example

A student is using a Geiger-counter to measure the counts per minute at different distances from a source of radiation. Their results and a graph of the results are shown here.

Background example, downloadable IGCSE & GCSE Physics revision notes

Determine the background radiation count.

Step 1: Determine the point at which the source radiation stops being detected

    • The background radiation is the amount of radiation received all the time
    • When the source is moved back far enough it is all absorbed by the air before reaching the Geiger-counter
    • Results after 1 metre do not change
    • Therefore, the amount after 1 metre is only due to background radiation

Step 2: State the background radiation count 

    • The background radiation count is 15 counts per minute

Measuring Radiation Dose

  • It is important to regulate the exposure of humans to radiation
  • The amount of radiation received by a person is called the dose and is measured in sieverts (Sv)
  • One sievert is a very big dose of radiation
    • It would cause acute radiation poisoning
  • People would normally receive about 3 mSv (0.003 Sv) in one year
  • To protect against over-exposure, the dose received by different activities is measured
  • A dosemeter measures the amount of radiation in particular areas

radiation-badge, IGCSE & GCSE Physics revision notes

A dosemeter, or radiation badge, can be worn by a person working with radiation in order to keep track of the amount of radiation they are receiving

Differences in Exposure

  • The level of background radiation and radiation dose may be affected by a person’s occupation or location
  • Some areas around the world have higher background radiation because they are closer to sources of radiation
  • People that work with nuclear radiation receive more radiation
    • The UK limit for nuclear industry employees is 20 mSv in one year
  • The diagram below compares the dose received by some different activities

Comparing dose, downloadable IGCSE & GCSE Physics revision notes

All living things emit a small amount of radiation: the amount of radiation within a banana is tiny, and not at all dangerous!

Exam Tip

You have been introduced to three different units to do with radiation:

  • Becquerels measure the amount of radiation emitted by a source every second
  • Counts per second measures the rate at which radiation hits a particular location
  • Sieverts measure the received dose of radiation

They are not the same thing!

Author: Katie

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.
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