AQA GCSE Combined Science Foundation (8464), Foundation tier · Physics › Atomic structure › Atoms and nuclear radiation
Practise Radioactive contamination. 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.
The difference between radioactive contamination and irradiation, why the type of radiation affects the hazard inside and outside the body, the precautions that reduce the risk, and why studies of radiation's effects are published and peer reviewed. Expect 'compare', 'explain' and 'give precautions' questions.
Key facts
Contamination = unwanted radioactive atoms on or in a material
Irradiation = exposure to radiation from an outside source
An irradiated object does NOT become radioactive
Outside the body: β and γ are more hazardous (can reach organs); α is absorbed by skin
Inside the body: α is most hazardous (strongly ionising, absorbed by nearby cells)
Precautions: tongs, gloves, lead-lined box, short time, keep your distance
Peer review: other scientists check published findings
Notes
Contamination and irradiation
Radioactive contamination is the unwanted presence of materials containing radioactive atoms on or in other materials, e.g. radioactive dust on skin, or radioactive gas breathed in.
The hazard comes from the decay of the contaminating atoms. It continues until the material is removed or has decayed, and removing it can be difficult.
Irradiation is exposing an object to nuclear radiation from a source outside it. The irradiated object does not become radioactive.
Irradiation stops as soon as the source is taken away or shielded.
How the type of radiation affects the hazard
diagram
Ionising radiation can damage or kill cells, and can change DNA, which may lead to cancer.
Outside the body: alpha is the least hazardous, because the air or the outer layer of dead skin absorbs it. Beta and gamma are more hazardous, because they can penetrate the skin and reach organs.
Inside the body (swallowed or breathed in): alpha is the most hazardous. It is strongly ionising, and all of its energy is absorbed by nearby cells, causing a lot of damage in one place.
Inside the body, gamma is the least hazardous, because it is weakly ionising and most of it passes out of the body.
Outside the body alpha is the least hazardous; inside the body it is the most hazardous.
Precautions
Handle sources with long tongs, to increase the distance between the source and your body.
Wear gloves to stop radioactive material getting onto your skin.
Keep sources in a lead-lined box, and take them out for as short a time as possible.
Never point a source at anyone. Workers wear a dosimeter badge to monitor the dose they receive.
Sharing findings
It is important that findings of studies into the effects of radiation on humans are published and shared with other scientists, so that they can be checked by peer review.
How to answer each type of question
Give precautions and explain them
2 to 4 marksGrade 4
Give a specific precaution (tongs, gloves, lead-lined box, short time).
Say how it reduces the risk: more distance, less time, shielding, or stops contamination.
Example. A teacher uses a radioactive source in a lesson. Give two precautions the teacher should take to reduce the risk to themselves. Explain how each precaution reduces the risk.
Show the model answerHide the model answer
Handles the source with long tongs (1), which keeps the source further from the body (1). Puts the source back in its lead-lined box as soon as possible (1), which reduces the time of exposure (and the lead absorbs the radiation) (1).
Don’t lose marks
Saying an irradiated object, such as sterilised equipment, becomes radioactive. It does not.
Saying alpha is 'not dangerous'. It is very dangerous inside the body.
Giving a precaution without saying how it reduces the risk, when the question asks you to explain.
Saying peer review means other scientists 'agree' with the findings. It means they check them.
More tips
Memory tricks
Contamination = the source is ON or IN you, so it goes where you go. Irradiation = the source is NEAR you; move away and it stops.
Alpha: least hazardous outside, most hazardous inside. Beta and gamma are the danger from outside.
Every precaution does one of four things: more distance, less time, shielding, or keeping the material off you.
Exam technique
In comparison questions, make each point about both: 'contamination ... whereas irradiation ...'.
Link the hazard to ionisation: 'strongly ionising', 'absorbed by cells', 'damages cells or DNA'.
For peer review, the key words are 'other scientists' and 'check'.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Give precautions for handling radioactive sourcesUse tongs, wear gloves, keep the source in a lead-lined box and spend as little time near it as possible.
Grade 4
Define contamination and irradiationContamination: unwanted radioactive material on or in something; irradiation: exposure to radiation from outside.
Grade 5
State that irradiation does not cause radioactivityAn irradiated object does not become radioactive.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Surgical instruments are sterilised by irradiating them with gamma rays. Do the instruments become radioactive?
No
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
(a) What is meant by radioactive contamination? Tick (✓) one box.[1]
The unwanted presence of materials containing radioactive atoms on or in other materials
Exposing an object to nuclear radiation
The decay of an unstable nucleus
The number of decays each second
(b) What is meant by irradiation? Tick (✓) one box.[1]
Exposing an object to nuclear radiation
Radioactive atoms getting onto an object
Heating an object with infrared radiation
An object absorbing light from the Sun
(c) Surgical instruments are sterilised by irradiating them with gamma rays. Do the instruments become radioactive?[1]
(d) Give one precaution a worker could take to avoid being contaminated when handling a radioactive liquid.[1]
Show the answer and mark scheme
(a)Answer: The unwanted presence of materials containing radioactive atoms on or in other materials
(b)Answer: Exposing an object to nuclear radiation
(c)Answer: No
no (an irradiated object does not become radioactive)
(d)Answer: Wear disposable gloves.
wear gloves / protective clothing
use tongs
wear a mask / work in a fume cupboard so that radioactive material is not breathed in
Question 2Medium6 marks
Polonium-210 emits alpha particles.
(a) Explain why a sample of polonium-210 is not very hazardous outside the body, but is extremely hazardous if it gets inside the body.[4]
(b) Explain why a person who has swallowed a radioactive substance is described as contaminated, not irradiated.[2]
Show the answer and mark scheme
(a)Answer: Outside, the alpha particles are stopped by air or dead skin and never reach living cells. Inside, they are absorbed by nearby living cells, and being strongly ionising they cause severe damage.
outside the body the alpha particles are absorbed by the air / by the outer layer of the skin
so they do not reach living cells
inside the body the alpha particles are absorbed by the (living) cells close to the source
alpha particles are strongly ionising, so they cause a lot of damage to these cells (e.g. to DNA, which can cause cancer)
(b)Answer: The radioactive atoms are now inside the body, so the exposure continues until they decay or are removed.
the radioactive atoms are inside the person’s body
so the person keeps being exposed to radiation until the atoms decay or leave the body (irradiation only happens while the person is near a source)