4.8 Uses and hazards of nuclear radiation
9 exam questions worth 27 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
0 / 27
Which type of radiation is used in a smoke alarm?
Choose one answer.
Correct Not quite: the answer is Alpha
Mark scheme
A: Alpha
Model answer
Alpha (A). Alpha is absorbed by smoke, but stopped by the alarm's case.
Why is a gamma source used to sterilise packaged surgical instruments?
Choose one answer.
Correct Not quite: the answer is Gamma rays are very penetrating and kill bacteria through the packaging
Mark scheme
B: Gamma rays are very penetrating and kill bacteria through the packaging
Model answer
Gamma rays are very penetrating and kill bacteria through the packaging (B).
A hospital uses a radioactive tracer to check how well a patient's kidneys work. Explain why the tracer should emit gamma rays and have a half-life of a few hours.
Mark scheme
gamma rays can pass out of the body (1); so they can be detected outside the body by a gamma camera / alpha would be absorbed (1); a short half-life means that the tracer lasts long enough for the scan (1); but it decays quickly, so the patient is not exposed for long / dose is small (1)
Model answer
Gamma rays pass out of the body so they can be detected by a camera outside, whereas alpha would be absorbed inside. A half-life of a few hours is long enough for the scan, but short enough that the patient is only exposed for a short time.
Explain how an external radiotherapy machine is able to destroy a tumour without causing too much damage to the healthy tissue around it.
Mark scheme
gamma rays are aimed at the tumour from different directions (1); the beams cross at the tumour so it receives the highest dose (1); healthy tissue is exposed to each beam for only a short time / receives a lower dose (1)
Model answer
The gamma source is moved around the patient so the beams reach the tumour from many directions. They all cross at the tumour, which gets a high dose, but the healthy tissue is only exposed to each beam briefly.
A smoke alarm contains americium-241, an alpha source with a half-life of 432 years. Explain why alpha radiation and a long half-life are suitable for this use.
Mark scheme
alpha is absorbed by smoke, so the current falls when smoke is present (1); alpha is stopped by air / the case so it is safe for people (1); a long half-life means that the source stays active for many years (1); so it does not need to be replaced / the alarm continues to work (1)
Model answer
Alpha particles are absorbed by smoke, so the alarm can sense it, but they are stopped by the alarm's case so they are safe in a house. The long half-life means the source keeps working for many years.
Cobalt-60 is a gamma emitter with a half-life of 5.3 years. Give two reasons why it is suitable for sterilising medical equipment.
Mark scheme
gamma is very penetrating so it can pass through the packaging (1); the half-life is long so the source does not need to be replaced often (1)
Model answer
Gamma rays penetrate the packaging and kill bacteria on the instruments inside. The half-life of 5.3 years is long enough for the source to be used for several years.
A technician is choosing a radioactive source to monitor the thickness of paper in a factory. The detector is on the opposite side of the paper to the source. Suggest which type of radiation is best and explain why.
Mark scheme
beta (1); alpha would be stopped by the paper (1); gamma would pass through the paper almost unchanged, so changes in thickness would not be detected (1)
Model answer
Beta radiation is best. Alpha would be completely absorbed by the paper, and gamma would go through it with almost no change, but beta is partly absorbed, so the count changes when the thickness of the paper changes.
(Edexcel) Describe how a PET scan produces an image of part of the body.
Mark scheme
a positron-emitting isotope is injected (into the patient) (1); a positron meets an electron and they annihilate (1); two gamma rays are produced travelling in opposite directions (1); detectors around the patient record the gamma rays and a computer builds up an image (1)
Model answer
A positron emitter is injected. Each positron meets an electron and they annihilate, producing two gamma rays in opposite directions. A ring of detectors picks up the gamma rays and a computer builds up an image.
Isotope W emits alpha particles and has a half-life of 10 days. Isotope X emits gamma rays and has a half-life of 6 hours. Isotope Y emits gamma rays and has a half-life of 5 years. Isotope Z emits beta particles and has a half-life of 3 days. Which isotope is best for a medical tracer, and which for sterilising equipment? Explain your choices.
Mark scheme
X for the tracer (1); gamma passes out of the body to be detected (1); short half-life so the patient's exposure is small (1); Y for sterilising (1); gamma penetrates the packaging and a long half-life means the source lasts / does not need to be replaced (1)
Model answer
Isotope X is best for a tracer because gamma rays leave the body to be detected, and the half-life of 6 hours is long enough for a scan but short enough for the patient's exposure to be small. Isotope Y is best for sterilising because gamma rays pass through packaging and the 5-year half-life means the source lasts for a long time.
Found a mistake?