Uses & Dangers of Radiation (Edexcel GCSE Physics): Flashcards
Exam code: 1PH0
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Define dose.
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Define dose.
The amount of radiation received by a person, measured in sieverts (Sv).
What is a dosimeter?
A device that measures the amount of radiation a person is exposed to, often worn by radiographers or others working with radiation.
How can ionising radiation lead to cancer?
It can ionise atoms in DNA, damaging the strand. If the DNA is repaired incorrectly it may mutate, and a mutated cell that replicates itself can form a tumour.
State two acute effects of radiation exposure on the body.
Skin burns, similar to severe sunburn, and a reduction in white blood cells, which increases susceptibility to infection.
Why can radiation used to treat cancer also damage healthy tissue?
High-energy radiation such as gamma rays and X-rays can damage healthy tissue if it is not properly targeted at the tumour.
State three ways of handling a radioactive source safely.
Any three from: keep it in a shielded container (e.g. lead-lined box) when not in use; use gloves and tongs; wear protective clothing; limit the time it is used for.
A person in the UK normally receives a dose of about 3 mSv of radiation per year. This is due to _____ radiation.
A person in the UK normally receives a dose of about 3 mSv of radiation per year. This is due to background radiation.
True or False?
A person is exposed to more radiation during a dental X-ray than during a transatlantic flight.
False.
A person is exposed to 0.005 mSv of radiation during a dental X-ray compared to 0.8 mSv of radiation during a transatlantic flight.
Therefore, a person is exposed to 160 times more radiation during a transatlantic flight than during a dental X-ray.
Define contamination.
The unwanted presence of materials containing radioactive atoms on other materials.
Define irradiation.
The process of exposing a material to alpha, beta or gamma radiation. It does not make the material radioactive.
Why is contamination generally more dangerous than irradiation?
Contamination causes continuous exposure to radiation as the radioactive atoms remain in place, and is especially dangerous if a source gets inside the body, where it irradiates internal organs as it moves through.
State one way of protecting against irradiation and one way of protecting against contamination.
Irradiation: lead-lined suits/shielding absorb the radiation.
Contamination: an airtight suit stops radioactive atoms getting inside the body.
Why does a source with a short half-life pose a greater risk of irradiation?
A short half-life means the source has a high activity, so there is a high rate of radioactive emissions compared with a long half-life source.
A source with a long half-life poses a greater risk of ______ because it remains radioactive for a long time.
A source with a long half-life poses a greater risk of contamination because it remains radioactive for a long time.
True or False?
Irradiating a piece of surgical equipment makes it radioactive.
False.
Irradiation does not make a material radioactive; only contamination, where radioactive atoms get onto or into a material, does this.
State four uses of radiation.
Any four from: diagnosis and treatment of cancer (radiotherapy); sterilising food; sterilising medical equipment; dating ancient artefacts; measuring the thickness of materials; smoke detectors.
Why is alpha radiation used in smoke detectors rather than beta or gamma?
Alpha is strongly ionising and weakly penetrating, so it normally ionises the air to create a current. Beta and gamma would pass straight through the smoke without being absorbed, so the alarm would not be triggered.
Why is beta radiation, rather than alpha or gamma, used to monitor the thickness of materials such as aluminium foil?
Beta is only partially absorbed by the material, so the number of particles reaching the detector changes with thickness. Alpha would be completely absorbed, and gamma would almost all pass through, giving no detectable difference.
Why is gamma radiation used to sterilise medical equipment?
Gamma is the most penetrating type of radiation, so it can irradiate all sides of the instruments and sterilise them without removing the packaging.
Define radiotherapy.
The treatment of cancer using radiation. Beams of gamma rays are directed at a tumour and moved around to minimise damage to healthy tissue.
Food can be ______ to kill microorganisms, making it last longer and reducing the risk of food-borne infection.
Food can be irradiated to kill microorganisms, making it last longer and reducing the risk of food-borne infection.
True or False?
As a material being thickness-gauged with beta radiation gets thicker, more particles are detected passing through it.
False.
As the material gets thicker, more particles are absorbed, so fewer particles get through to the detector.
The dangers of ionising radiation depend on the _____ of the isotope.
The dangers of ionising radiation depend on the half-life of the isotope.
Why can it be advantageous to use a small amount of a short-half-life isotope?
It emits a lot of radiation quickly but then rapidly loses its radioactivity, whereas a large amount could be extremely dangerous to handle.
Why is radioactive waste with a long half-life buried underground?
It remains radioactive for a very long time, so burial prevents it from being released into the environment.
Why does a source with a short half-life pose a greater risk of irradiation than one with a long half-life?
A short half-life means the source has a high activity, so there is a high rate of radioactive emissions compared with a long half-life source.
A source with a long half-life poses a greater risk of ______ because it remains radioactive for a long time.
A source with a long half-life poses a greater risk of contamination because it remains radioactive for a long time.
Define tracer.
A radioactive isotope used to track the movement of a substance, such as blood, around the body. A gamma emitter is usually chosen.
State two reasons why gamma emitters are used as medical tracers rather than alpha or beta emitters.
Gamma rays are highly penetrating, so they can pass out of the body and be detected externally. Gamma is also less ionising, minimising harm to the patient.
Why must a medical tracer have a short half-life of around a few hours?
Long enough to carry out the procedure, but not so long that it causes long-term harm to the patient.
Describe how a PET scanner detects a tracer inside the body.
Positrons emitted by the tracer travel a short distance and annihilate with electrons in the tissue, producing a pair of gamma-ray photons that are detected outside the body.
What is the difference between external and internal radiotherapy?
External radiotherapy directs beams of gamma rays at a tumour from outside the body. Internal radiotherapy inserts small pellets of radioactive material directly into the tumour.
Why are isotopes used in medical procedures produced close to the hospital that will use them?
Because they have short half-lives, so if produced far away they would decay too much before arriving and become unusable.
During external radiotherapy, beams are moved around the tumour to minimise damage to ______ tissue.
During external radiotherapy, beams are moved around the tumour to minimise damage to healthy tissue.
True or False?
In PET scanning, the tracer itself emits the gamma rays that are detected outside the body.
False.
The tracer emits positrons, which annihilate with electrons in the tissue to produce the gamma-ray photons that are detected.
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