Doctors in a hospital use two different regions of the electromagnetic spectrum: X-rays to image a patient's broken bone, and gamma rays to treat a cancerous tumour. (a) State why both X-rays and gamma rays must be used carefully, in terms of their effect on living cells. [1] (b…

Answer: ((a)) X-rays and gamma rays are ionising radiation and can damage or kill living cells, or cause mutations that may lead to cancer ((b)) the lead screen absorbs the X-rays, and leaving the room increases the radiographer's distance from the source; both reduce the radiographer's dose, which matters because they are exposed repeatedly, unlike a patient having a single X-ray ((c)) e.g. security scanning of luggage at airports, or industrial inspection of welds/metal castings for internal flaws. Part (a): Why X-rays and gamma rays must be used carefully X-rays and gamma rays are both forms of ionising radiation: they carry enough energy to remove electrons from atoms and break chemical bonds. In living tissue this can damage or ki…

IGCSE Physics 0625: Uses and Safety of X-rays and Gamma Rays

Part (a): Why X-rays and gamma rays must be used carefully

X-rays and gamma rays are both forms of ionising radiation: they carry enough energy to remove electrons from atoms and break chemical bonds. In living tissue this can damage or kill cells, or cause mutations in DNA that may lead to cancer. This is why their use must always be carefully controlled.

Part (b): Why the radiographer takes precautions

A single X-ray photograph exposes a patient to only a small, occasional dose of radiation, so the risk to the patient from one scan is low. A radiographer, however, is present for many X-rays every working day, so their radiation dose builds up over months and years of repeated exposure.

Standing behind a lead screen, or leaving the room, protects the radiographer because:

lead absorbs X-rays very effectively, so the screen blocks most of the radiation that would otherwise reach the radiographer, and
leaving the room (or standing further away) reduces the intensity of radiation reaching them, since intensity falls off with distance from the source.

Both measures reduce the radiographer’s cumulative dose, keeping their long-term exposure to ionising radiation as low as reasonably possible.

Part (c): A non-medical use of X-rays

X-rays are also used outside medicine, for example:

security scanning of luggage at airports, where X-ray images reveal the contents of bags without opening them, or
industrial inspection of welds or metal castings, to detect internal cracks or flaws that are not visible from the outside.

Any one correct non-medical use earns the mark.

Final answers

(a) X-rays and gamma rays are ionising radiation, which can damage living cells or cause mutations
(b) The lead screen/leaving the room reduces the radiographer’s dose. Necessary because, unlike a patient, they are repeatedly exposed over their career
(c) Non-medical use of X-rays $=$ e.g. airport security scanning / industrial flaw detection