4.4 Background radiation and detecting radiation
9 exam questions worth 16 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Which is the largest source of background radiation in the UK?
Choose one answer.
Correct Not quite: the answer is Radon gas
Mark scheme
C: Radon gas
Model answer
Radon gas (C).
What is the unit of radiation dose?
Choose one answer.
Correct Not quite: the answer is Sievert
Mark scheme
B: Sievert
Model answer
Sievert (B). The becquerel is the unit of activity.
State two natural sources of background radiation.
Mark scheme
any two from: radon gas / rocks / the ground and buildings / food and drink / cosmic rays (1 each)
Model answer
Radon gas from rocks, and cosmic rays from space.
State one man-made source of background radiation.
Mark scheme
medical X-rays / gamma scans / nuclear weapons testing / nuclear accidents / nuclear power
Model answer
Medical X-rays.
A student measures a background count rate of 24 counts per minute. With a source in place, the count rate is 312 counts per minute. Calculate the corrected count rate.
Mark scheme
corrected count rate = 312 − 24 (1); 288 counts per minute (1)
Model answer
Corrected count rate = 312 − 24 = 288 counts per minute.
Explain why a student should measure the background count for several minutes and take a mean, rather than taking one short reading.
Mark scheme
radioactive decay is random (1); so the count varies, and a mean gives a more reliable / accurate value (1)
Model answer
Radioactive decay is random, so the count varies from one reading to the next. A long measurement and a mean gives a more reliable value.
Explain why airline pilots receive a higher radiation dose than people who work in offices.
Mark scheme
they fly at high altitude where there is less atmosphere / air to absorb cosmic rays (1); so they are exposed to more cosmic radiation (1)
Model answer
At high altitude there is less air above to absorb cosmic rays, so pilots are exposed to more cosmic radiation.
Describe how a Geiger-Müller tube detects radiation.
Mark scheme
radiation enters through the window of the tube (1); it ionises the gas inside (1); this produces a pulse of current that is counted by the counter (1)
Model answer
Radiation enters the tube and ionises the gas inside it. This gives a brief pulse of current, and each pulse is counted by the counter.
A worker in a nuclear power station wears a badge containing photographic film. Explain how the film shows how much radiation the worker has been exposed to.
Mark scheme
radiation darkens the film (1); the more radiation received, the darker the film when it is developed (1)
Model answer
Radiation darkens the film, so when it is developed, the darker it is, the more radiation the worker has received.
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