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 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.
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
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.
