Background Radiation (AQA GCSE Physics)

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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

What is Background Radiation?

  • Background radiation is defined as:

The radiation that exists around us all the time

Sources of Background Radiation

  • 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 notesDetermine 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

Ashika, Physics Project Lead

Teacher tip

Ashika

Physics Project Lead

Students often ask me if background radiation is the same as cosmic microwave background radiation (CMBR). It's a great question because it shows that they are trying to find links between concepts and deepen their understanding. Background radiation and CMBR do sound similar, but they are not the same thing. I think the confusion arises because cosmic rays are also a contributing factor of background radiation. 

Background radiation is the constant low-level radiation we all all exposed to on Earth every day. Radiation is released from the decay of tiny amounts of radioactive substances (like uranium) in the rocks below ground, these tiny amounts of radioactive substances can end up in our food and water as well. 

Cosmic rays are particles that travel from the Sun or nearby stars, that are mainly protons or small nuclei. Cosmic rays interact with the Earth's atmosphere sending showers of smaller particles down toward the Earth's surface providing a constant low-level source of radiation. 

Cosmic Microwave Background Radiation is radiation from the Big Bang explosion that is still travelling outwards across the Universe. CMBR is an EM wave that has been stretched out over time to the microwave region of the EM spectrum. 

Cosmic rays and CMBR are beyond the scope of AQA GCSE Physics, but by learning just a little about each, you can see that background radiation and CMBR are completely different phenomena.

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-and-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!

Examiner 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!

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Ashika

Author: Ashika

Expertise: Physics Project Lead

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.