Practise Radioactive contamination. 11 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.
Grade by grade
What you need to be able to do, from the first marks up to the top 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.
4
Define contamination and irradiationContamination: unwanted radioactive material on or in something; irradiation: exposure to radiation from outside.
5
State that irradiation does not cause radioactivityAn irradiated object does not become radioactive.
6
Explain why findings are peer reviewedPublished findings can be checked by other scientists, so the conclusions are more reliable.
6
Compare the hazards of contamination and irradiationContamination keeps exposing you until it is removed or decays; irradiation stops when the source is removed.
7
Explain which radiation is most hazardous whereOutside the body beta and gamma are more hazardous; inside the body alpha is most hazardous.
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
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.
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.
Cheatsheet
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
How to answer each type of question
Give precautions and explain them
2 to 4 marks4
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 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).
Compare contamination and irradiation
3 marks6
Define each one in a sentence.
Say how long the exposure lasts in each case.
Say whether the object or person becomes radioactive.
Example. Compare the hazards of contamination and irradiation.
Show the model answer
Contamination is radioactive material getting onto or into a person or object, whereas irradiation is exposure to radiation from a source outside them (1). A contaminated person keeps receiving radiation until the material is removed or has decayed (1). An irradiated person stops receiving radiation as soon as the source is removed or shielded, and does not become radioactive (1).
Explain why findings are shared
2 marks6
Say that other scientists can check (or repeat) the work: peer review.
Say why that matters: the conclusions can be trusted and used for safety.
Example. Scientists have studied the health of people exposed to radiation. Explain why it is important that these findings are published.
Show the model answer
So that other scientists can check the findings (peer review) (1). This makes the conclusions more reliable, so they can be used to set safe limits for radiation doses (1).
Explain the hazard inside and outside the body
3 marks7
Say what absorbs the radiation when the source is outside the body.
Say what absorbs it when the source is inside the body.
Link the ionising power to the damage done to cells or DNA.
Example. Radon is a radioactive gas that emits alpha particles. Explain why radon is more hazardous when it is breathed in than when it is outside the body.
Show the model answer
Outside the body, the alpha particles are absorbed by the air or the outer layer of skin, so they do not reach living cells (1). Inside the lungs, the alpha particles are absorbed by nearby cells (1). Alpha is strongly ionising, so it damages these cells or their DNA, which may lead to cancer (1).
Shortcuts and 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.
Where marks are lost
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.
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'.
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)
Question 3Hard7 marks
Some foods are irradiated with gamma rays to kill bacteria. This makes the food last longer. Some people think that irradiated food is dangerous to eat.
(a) Explain why gamma rays are used rather than alpha or beta radiation.[2]
(b) A shopper says: ‘I will not eat irradiated food because it will be radioactive.’ Evaluate the shopper's statement.[3]
(c) Explain why food that is contaminated with a radioactive isotope is much more hazardous than food that has been irradiated.[2]
Show the answer and mark scheme
(a)Answer: Gamma rays penetrate the packaging and the whole of the food, so they reach all the bacteria.
gamma rays are very penetrating / can pass through the packaging and the food
so they can reach bacteria throughout the food (alpha and beta would be absorbed near the surface)
(b)Answer: Wrong: irradiation only exposes the food to gamma rays; no radioactive atoms are added, so the food does not become radioactive.
irradiated food does not become radioactive
because the food is only exposed to radiation; no radioactive atoms are added to the food (it is not contaminated)
so the shopper is wrong: the food does not emit radiation after irradiation
(c)Answer: Eating contaminated food puts radioactive atoms inside the body, where they keep emitting radiation.
contaminated food contains radioactive atoms, which would be eaten / get inside the body
the atoms keep decaying and emitting radiation inside the body until they decay or are removed