✓ Revise Right course
Radiation dose is measured in sieverts (Sv), and a millisievert (mSv) is one thousandth of a sievert. Free GCSE AQA Physics notes and 15 questions answered.
Radiation Dose and Measurement is part of Hazards and uses of radioactive emissions and of background radiation (physics only) in GCSE AQA Higher Physics.
6 min
Reading time
23
Lessons in this topic
GCSE AQA Higher
Pathway
Reviewed by Revise Right
Content review
Radiation dose is measured in sieverts (Sv), and a millisievert (mSv) is one thousandth of a sievert. Free GCSE AQA Physics notes and 15 questions answered.
AQA GCSE Physics mock draft, 26–31 Oct. Draft coverage: Physics Paper 1 (Higher tier). Reviewed for an original-practice sitting; check student availability before registering. Marking and results will follow later, after separate approval. Eligible new accounts receive a five-day Pro trial when signup email verification completes. Previous trials keep their original expiry. After expiry, new papers need Pro unless you have an explicitly confirmed free sitting offer for this event. That offer adds no Pro time or AI learning. Saved attempts and released results remain readable. No card or automatic charge.
Use this lesson to stay inside Hazards and uses of radioactive emissions and of background radiation (physics only) while connecting the detail back to the wider Atomic structure topic.
Read the core explanations from Radiation Dose and Measurement before testing yourself from memory.
Every day, you're exposed to invisible radiation from space, rocks, and even bananas. But how do we measure whether this exposure is safe or dangerous? This is where radiation dose becomes crucial - it's the key to understanding radiation safety in medicine, nuclear power, and everyday life.
Radiation dose tells us how much ionising radiation your body actually absorbs, not just how much is around you. Think of it like the difference between standing in the rain and measuring how wet you get - the dose is how wet you actually become, not just how heavy the rainfall is.
The clever thing about radiation dose is that it accounts for different types of radiation having different effects on your body. Alpha particles cause more biological damage per unit of energy than gamma rays, so the dose measurement adjusts for this difference.
The sievert (Sv) is named after Swedish physicist Rolf Sievert, who pioneered radiation protection. Unlike simple energy measurements, the sievert accounts for how different types of radiation affect living cells differently.
One sievert is actually a very large dose - enough to cause serious radiation sickness. That's why we usually work with much smaller units in everyday situations. Most medical procedures and occupational exposures are measured in millisieverts.
The conversion is straightforward: 1000 millisieverts = 1 sievert. This is similar to how 1000 millimetres = 1 metre. Most chest X-rays give you about 0.1 mSv, while a CT scan might be 10-20 mSv.
Worked example: Converting Between Sieverts and Millisieverts
A nuclear worker receives an annual dose of 15 mSv. Express this in sieverts.
Answer: 0.015 Sv
You can't escape background radiation - it's everywhere. This low-level radiation comes from cosmic rays, radioactive elements in rocks and soil, and human activities like nuclear weapons testing and power generation.
The average person in the UK receives about 2.7 mSv per year from background radiation. About 85% comes from natural sources, with radon gas from granite rocks being the biggest contributor. The remaining 15% comes from artificial sources, mainly medical procedures.
Background radiation isn't uniform across the country. Areas with granite bedrock, like Cornwall and parts of Scotland, have higher levels because granite contains naturally radioactive uranium. Coastal areas might have slightly higher cosmic ray exposure due to less atmospheric shielding.
**Trap**: Many students think background radiation is dangerous because it's 'radioactive'. Actually, these natural levels are what life on Earth evolved with - they're part of our normal environment and generally pose minimal risk.
Where you live dramatically affects your radiation exposure. Geography, geology, and altitude all play crucial roles in determining your annual dose.
Altitude matters because there's less atmosphere to shield you from cosmic rays. Airline pilots and frequent flyers receive significantly higher doses than ground-based workers. A return flight from London to New York adds about 0.08 mSv to your annual dose.
Geology is even more important. Areas built on granite bedrock have higher radon levels because granite contains uranium, which decays to produce radon gas. This gas seeps into buildings through foundations and can accumulate to significant levels, especially in poorly ventilated spaces.
Some parts of Cornwall receive over 10 mSv per year from natural background radiation - nearly four times the UK average. Residents aren't at immediate risk, but long-term exposure to elevated radon levels does increase lung cancer risk, particularly for smokers.
Some jobs inevitably involve higher radiation exposure. Nuclear power workers, radiographers, airline crew, and even some miners face occupational doses well above background levels.
Nuclear industry workers are strictly monitored and limited to 20 mSv per year - about seven times the average background dose. They wear dosimeters (radiation detectors) that continuously monitor their exposure, and detailed records are kept throughout their careers.
Medical workers using X-rays or radioisotopes also face elevated exposure. A radiographer might receive 2-5 mSv per year, while interventional cardiologists (who use X-ray guidance during heart procedures) can receive 10-15 mSv annually.
Surprisingly, airline crew receive some of the highest occupational doses. Flying at 35,000 feet means much less atmospheric protection from cosmic radiation. Long-haul pilots and cabin crew can receive 4-6 mSv per year - more than many nuclear workers.
**Trap**: Students often assume nuclear workers get the highest doses. Actually, some medical workers and airline crew receive higher annual exposures due to the nature of their work and the difficulty of shielding against cosmic rays or medical X-rays.
Understanding radiation doses helps you make informed decisions about medical procedures and assess real risks. A chest X-ray (0.1 mSv) gives you about the same dose as 10 days of natural background radiation.
CT scans deliver much higher doses - typically 10-20 mSv, equivalent to several years of background radiation. However, the medical benefit usually far outweighs the small increased cancer risk, especially for older patients where the benefit is immediate but cancer risk is long-term.
Nuclear accidents provide dramatic examples of high doses. Chernobyl emergency workers received doses of 100-500 mSv, causing acute radiation sickness in many cases. The general public in affected areas received much lower doses, typically 10-50 mSv over several years.
For comparison, a dose of 1000 mSv (1 Sv) received quickly would cause radiation sickness with nausea, fatigue, and reduced white blood cell count. Doses above 4-5 Sv are often fatal without medical treatment. These levels are thousands of times higher than typical medical or occupational exposures.
Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-03-20.
Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
Radiation dose is measured in sieverts (Sv), the SI unit that takes into account both the energy absorbed and the biological effectiveness of different types of radiation. One sievert is a very large dose, so millisieverts (mSv), one thousandth of a sievert, are commonly used.
A sievert (Sv) is the SI unit for measuring radiation dose, taking into account both the energy absorbed and the biological effectiveness of different types of radiation. One sievert is a very large dose, enough to cause serious radiation sickness.
A millisievert (mSv) is one thousandth of a sievert (0.001 Sv), the unit commonly used for typical radiation doses in medicine and occupational exposure. A chest X-ray gives about 0.1 mSv.
Radiation dose is a measure of the amount of ionising radiation absorbed by living tissue, taking into account the biological damage it can cause. It is measured in sieverts (Sv) and adjusts for alpha particles causing more damage per unit of energy than gamma rays.
To convert millisieverts to sieverts, divide by 1000, because 1000 mSv = 1 Sv. A nuclear worker's annual dose of 15 mSv is 15 ÷ 1000 = 0.015 Sv.
Radon gas from granite rocks is the biggest contributor to UK background radiation. About 85% of the 2.7 mSv average yearly dose comes from natural sources, and the remaining 15% from artificial sources, mainly medical procedures.
Location affects radiation dose through altitude and geology. Higher altitude means less atmosphere to shield cosmic rays, and areas on granite bedrock, like Cornwall and parts of Scotland, have higher radon levels because granite contains uranium.
Jobs with higher radiation doses include nuclear power workers, radiographers, airline crew and some miners. Nuclear workers are limited to 20 mSv per year, while long-haul pilots and cabin crew can receive 4-6 mSv per year from cosmic radiation, more than many nuclear workers.
The sievert is named after Swedish physicist Rolf Sievert, who pioneered radiation protection. It is the SI unit of radiation dose, and it takes into account the biological effectiveness of different types of radiation.
Nuclear industry workers are strictly limited to 20 mSv per year, about seven times the average background dose. They wear dosimeters that continuously monitor their exposure, and detailed records are kept throughout their careers.
Long-haul pilots and cabin crew can receive 4–6 mSv per year, more than many nuclear workers, because flying at 35,000 feet means much less atmospheric protection from cosmic radiation.
A dose of 1000 mSv (1 Sv) received quickly would cause radiation sickness, with nausea, fatigue and a reduced white blood cell count. Doses of 4–5 Sv or more are often fatal without medical treatment.
A chest X-ray (0.1 mSv) gives about the same dose as 10 days of natural background radiation. A CT scan typically delivers 10–20 mSv, equivalent to several years of background radiation.
Radiation dose depends on the type of radiation because different types have different effects on the body. Alpha particles cause more biological damage per unit of energy than gamma rays, so the dose in sieverts adjusts for this.
Some parts of Cornwall receive over 10 mSv per year from natural background radiation, nearly four times the UK average, because granite contains uranium that decays to radon gas. Long-term exposure to elevated radon increases lung cancer risk, particularly for smokers.