AQA GCSE Physics Foundation (8463), Foundation tier · Atomic structure › Hazards and uses of radiation
Practise Background radiation. 7 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
What background radiation is, where it comes from, why the dose people receive depends on their job and where they live, and the unit of radiation dose. Expect recall and data questions, often with a table or pie chart of sources. GCSE Physics only, not in Combined Science.
Key facts
Background radiation: radiation around us all the time
Natural sources: rocks (radon gas), cosmic rays, food and drink
Man-made sources: fallout from nuclear weapons testing and nuclear accidents
Radiation dose (risk of harm) is measured in sieverts (Sv)
Background radiation is around us all the time. A detector always records a low count rate, even with no source nearby.
Natural sources: rocks (some release radon, a radioactive gas), cosmic rays from space, and radioactive isotopes in food, drink and our own bodies.
Man-made sources: fallout from nuclear weapons testing and from nuclear accidents. Medical procedures such as X-rays also add to the dose people receive.
Most of the background radiation we receive comes from natural sources.
Approximate shares of the average yearly dose in the UK (figures vary between sources). Most of it is natural; radon gas is the biggest part.
Radiation dose
Radiation dose is a measure of the risk of harm to the body from exposure to radiation.
It is measured in sieverts (Sv). 1000 millisieverts (mSv) = 1 sievert. You do not need to recall the unit, but you must be able to use it.
The level of background radiation, and your radiation dose, can depend on your occupation and your location.
Occupation: aircrew spend many hours at high altitude, where cosmic rays are stronger. Nuclear industry workers, radiographers and miners may also receive higher doses.
Location: areas with granite rocks, which release radon, have more background radiation. So do high places, which receive more cosmic rays.
Correcting for background
A detector measuring a source also picks up background radiation.
Measure the background count rate with no source present, then subtract it from every reading.
Check whether the question wants natural or man-made sources.
Give a specific source, e.g. 'radon gas from rocks' rather than just 'the ground'.
Example. Give one natural source and one man-made source of background radiation.
Show the model answerHide the model answer
Natural: cosmic rays / rocks / radon gas (1) Man-made: fallout from nuclear weapons testing / nuclear accidents (1)
Correct a count rate for background
2 marksGrade 5
Find the background count rate (the reading with no source).
Subtract it from the reading with the source, keeping the same units.
Example. With no source present, a detector records 45 counts in one minute. With a source present, it records 510 counts per minute. Calculate the count rate due to the source alone.
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510 − 45 (1) = 465 counts per minute (1)
Don’t lose marks
Forgetting to subtract the background count rate when finding the count rate from a source.
Naming mobile phones, microwaves or Wi-Fi as sources of background radiation. They do not give out nuclear radiation.
Converting the wrong way: 0.008 Sv is 8 mSv, not 8000 mSv.
Saying most background radiation is man-made. Most is natural.
More tips
Memory tricks
Sources from the ground up: rocks and radon below you, food and drink inside you, cosmic rays above you.
milli means one thousandth: to change Sv into mSv, multiply by 1000.
If a question gives a reading 'with no source present', that is the background count: subtract it.
Exam technique
For 'suggest why' questions on dose, name the source (cosmic rays, radon) and link it to the job or place.
Read pie charts and tables carefully: natural sources may be split into several parts that you need to add.
Write the unit with every dose, and check whether the answer should be in Sv or mSv.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Define background radiationRadiation that is around us all the time, from natural and man-made sources.
Grade 4
Name natural sources of background radiationRocks (including radon gas released from rocks) and cosmic rays from space.
Grade 4
Name man-made sources of background radiationFallout from nuclear weapons testing and from nuclear accidents.
Grade 5
Correct a count rate for backgroundSubtract the background count rate from the measured count rate.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Background radiation is around us all of the time. Give two natural sources of background radiation.
Rocks (and the radon gas released from them) and cosmic rays.
Suggest why the dose from cosmic rays is higher at the height at which aircraft fly than at ground level.
There is less air above to absorb the cosmic rays.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Background radiation is around us all of the time.
(a) Give two natural sources of background radiation.[2]
(b) Give one man-made source of background radiation.[1]
(c) Radiation dose is measured in sieverts (Sv). 1000 millisieverts (mSv) = 1 sievert (Sv) The average annual radiation dose for a person in the UK is about 2.7 mSv. Give 2.7 mSv in sieverts.[1]
Show the answer and mark scheme
(a)Answer: Rocks (and the radon gas released from them) and cosmic rays.
rocks / the ground / building materials
cosmic rays (from space)
radon gas (from rocks)
food and drink / radioactive isotopes inside our bodies
(b)Answer: Fallout from nuclear weapons testing.
fallout from nuclear weapons testing
nuclear accidents
medical uses of radiation (e.g. X-rays)
waste / discharges from the nuclear industry
(c)Answer: 0.0027 Sv
0.0027 (Sv)
Question 2Medium5 marks
Airline pilots receive a higher dose of radiation than most people. At the height at which aircraft fly, the dose from cosmic rays is about 0.005 mSv per hour.
(a) Suggest why the dose from cosmic rays is higher at the height at which aircraft fly than at ground level.[1]
(b) A pilot flies for 700 hours in one year. Calculate the dose from cosmic rays that the pilot receives while flying in that year.[2]
(c) Give one other occupation in which a person may receive a higher radiation dose than average.[1]
(d) The annual dose limit for people who work with radiation is 20 mSv. The average annual dose from background radiation is 2.7 mSv. Explain whether the pilot’s dose is a cause for concern.[1]
Show the answer and mark scheme
(a)Answer: There is less air above to absorb the cosmic rays.
there is less atmosphere above the aircraft to absorb the cosmic rays
(b)Answer: 3.5 mSv
700 × 0.005
3.5 (mSv)
(c)Answer: A radiographer in a hospital.
hospital worker using radiation / radiographer
nuclear power station worker
miner
astronaut
(d)Answer: Not a major concern: about 6.2 mSv a year in total, well below the 20 mSv limit.
no: the total of about 6.2 mSv (3.5 + 2.7) is well below the 20 mSv limit (although any dose slightly increases the risk)