How is radioactivity used safely and beneficially, and what are its dangers?
Describe uses of radioactivity, its dangers to living cells, and safe handling and storage
A focused answer to the O-Level Physics outcome on uses and hazards of radiation. Medical and industrial uses, the dangers of ionising radiation to living cells, background radiation, and safe handling, shielding, and storage.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
SEAB wants you to describe useful applications of radioactivity in medicine and industry, to explain why ionising radiation is dangerous to living cells, to know about background radiation, and to state safe handling and storage precautions. The big idea is that radiation is a powerful tool that must be used carefully because it can damage living tissue.
The answer
Uses of radioactivity
Radioactivity has many beneficial uses, each chosen to match the type and half-life of the radiation:
- Medical imaging: a radioactive tracer is swallowed or injected and followed with a detector to image organs.
- Treating cancer (radiotherapy): focused gamma rays kill cancer cells.
- Sterilising: gamma rays kill bacteria on medical equipment and some foods, without heating.
- Thickness monitoring: a source and detector on opposite sides of a sheet control its thickness automatically.
- Smoke detectors: a weak alpha source ionises the air to detect smoke.
- Carbon dating: the decay of carbon-14 finds the age of ancient remains.
Why ionising radiation is dangerous
Ionising radiation knocks electrons off atoms in living cells, damaging important molecules such as DNA. This can:
- kill cells outright (high doses cause radiation burns and sickness),
- cause cells to mutate, which may lead to cancer.
Background radiation
Background radiation is the low-level ionising radiation that is always present around us. Sources include radon gas from rocks and soil, cosmic rays from space, food and drink, and artificial sources such as medical X-rays. It must be subtracted when measuring a source's true activity.
Safe handling and storage
To reduce exposure, those working with radioactive sources should:
- handle sources with tongs or remote handling tools, never bare hands,
- keep the exposure time as short as possible,
- keep a large distance from the source where possible,
- use shielding such as lead or concrete, and store sources in lead-lined containers,
- never point a source at people and wear monitoring badges.
Examples in context
Example 1. Radiotherapy. A beam of gamma rays is aimed at a tumour from several directions, so the tumour receives a high dose while the surrounding healthy tissue, on the path of only one beam, receives much less. This uses the cell-killing power of radiation deliberately, with careful planning to protect healthy cells.
Example 2. Food irradiation. Some foods are exposed to gamma rays to kill bacteria and extend shelf life. Because gamma rays pass right through the sealed packaging, the food can be sterilised after it is wrapped, without heating it or leaving any source inside, making it safe to eat.
Try this
Q1. State one medical and one industrial use of radioactivity. [2 marks]
- Cue. Medical: radiotherapy or tracers. Industrial: thickness monitoring or sterilising equipment.
Q2. Explain why ionising radiation is harmful to the body. [2 marks]
- Cue. It ionises atoms in cells and damages molecules such as DNA, which can kill cells or cause mutations leading to cancer.
Q3. State three precautions for handling a radioactive source safely. [3 marks]
- Cue. Limit the exposure time, keep a distance (use tongs), and use shielding such as lead, storing the source in a lead-lined container.
Exam-style practice questions
Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Original4 marks(a) State one use of radiation in medicine and one use in industry. (b) Explain why ionising radiation is dangerous to living cells.Show worked answer →
(a) Medicine: gamma rays are used to kill cancer cells (radiotherapy), or a tracer is used to image inside the body. Industry: a radioactive source is used to monitor the thickness of sheets, or gamma rays sterilise equipment. (Any one each.)
(b) Ionising radiation can knock electrons off atoms in living cells, damaging molecules such as DNA. This can kill cells or cause them to mutate, which may lead to cancer.
Markers reward a valid medical use and a valid industrial use, and the explanation that radiation ionises and damages cells (and DNA), which can kill them or cause cancer.
Original4 marks(a) State what is meant by background radiation, and give two sources of it. (b) State two precautions a worker should take when handling a radioactive source.Show worked answer →
(a) Background radiation is the low-level ionising radiation that is always present around us, from natural and artificial sources. Two sources: radon gas from rocks and soil, cosmic rays from space, or radiation from medical X-rays. (Any two.)
(b) Precautions: handle the source with tongs or a long handle to keep it away from the body; keep exposure time short; store it in a lead-lined container; wear protective clothing or use shielding; never point it at people. (Any two.)
Markers reward background radiation as the ever-present low-level radiation with two valid sources, and two sensible safety precautions such as using tongs and limiting exposure time.
Related dot points
- Describe alpha, beta, and gamma radiation and compare their nature, penetration, and ionising power
A focused answer to the O-Level Physics outcome on radioactivity. Radioactive decay from unstable nuclei, the nature of alpha, beta, and gamma radiation, their penetrating and ionising power, and how each is stopped.
- Define half-life and use it to calculate remaining activity or the number of undecayed nuclei
A focused answer to the O-Level Physics outcome on half-life. The meaning of half-life, the random nature of decay, reading a decay curve, and calculating remaining activity or undecayed nuclei after a number of half-lives.
- Describe the nuclear model of the atom and use proton number, nucleon number, and isotopes
A focused answer to the O-Level Physics outcome on atomic structure. The nuclear model with protons, neutrons, and electrons, proton and nucleon numbers, nuclide notation, and what isotopes are.
- Apply the relationships for electrical power and energy and describe fuses, earthing, and circuit safety
A focused answer to the O-Level Physics outcome on electrical power, energy, and safety. The power relationships, calculating energy and cost, and the roles of fuses, earthing, and switches in keeping mains circuits safe.