OCR GCSE Physics A: Uses and hazards of electromagnetic radiation (J249) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover statements P5.2g to P5.2j of the OCR GCSE (9-1) Gateway Science Physics A specification (J249, Version 5.0, July 2026). Questions 8 to 12 test P5.2i and are marked (Higher Tier only). The other questions are for both tiers. Where a question needs the speed of ultrasound it is given in the question.

Links: OCR GCSE Physics hub, printable checklist, study guide and revision notes.

Questions

1. Name the type of electromagnetic wave best suited to each job: (i) sending a signal to a television satellite, (ii) checking a banknote for a hidden marking, (iii) treating a tumour deep in the body, (iv) a thermal imaging camera looking for heat escaping from a house. [4]

2. Explain why a microwave oven heats a bowl of soup but a plastic bowl stays much cooler. [3]

3. A tanning salon uses lamps that give out ultraviolet waves.

(a) Describe two hazards to a customer’s body from ultraviolet. [2] (b) Suggest two ways a customer can reduce the risk when outdoors in strong sunshine. [2]

4. A radiographer takes X-ray images of many patients each day and stands behind a screen. Explain why the screen is needed for the radiographer but a patient has one image without a screen between the machine and them. [3]

5. Gamma rays are used in radiotherapy. The beam is directed at a tumour from several different directions.

(a) Explain why gamma rays can be used to treat cancer. [2] (b) Explain the advantage of using several directions. [2] (c) State one reason why staff operate the machine from another room. [1]

6. Describe how a radio programme is sent from a transmitter and detected by a portable radio. [4]

7. Gamma rays are used to sterilise packaged surgical gloves.

(a) Give two reasons why gamma rays suit this job. [2] (b) Explain why the packs are treated in a room with thick shielding and no staff present. [2]

8. (Higher Tier only) An X-ray image of a child’s wrist shows a thin dark line across a pale bone. Explain how the image is formed and what the dark line shows. [4]

9. (Higher Tier only) Ultrasound is used to scan an unborn baby.

(a) Explain how echoes from the baby are used to build up an image. [3] (b) Explain why gel is spread on the skin. [1] (c) Suggest why ultrasound is used instead of X-rays for this scan. [2]

10. (Higher Tier only) A pulse of ultrasound travels through soft tissue at 1500 m/s. Echoes come back from two boundaries, the first after 48 microseconds and the second after 132 microseconds. (1 microsecond = 10⁻⁶ s.)

(a) Calculate the depth of the first boundary. [2] (b) Calculate the depth of the second boundary. [2] (c) Calculate the distance between the boundaries. [1]

11. (Higher Tier only) A doctor wants to check a patient’s inflamed ankle.

(a) Explain why a thermal imaging camera can show the inflammation on the skin. [2] (b) Explain why infrared cannot be used to find a fracture in the ankle bone. [2]

12. (Higher Tier only) For each patient, name a suitable imaging method and explain your choice. (a) A pregnant woman needs her baby’s position checked. [3] (b) A cyclist may have a broken bone in the lower leg. [3] (c) A patient swallows a tracer so that the way a deep organ is working can be seen. [2]

Answers

1. (i) Microwaves [1]. (ii) Ultraviolet [1]. (iii) Gamma rays [1]. (iv) Infrared [1]. [4] Examiner insight: Answers naming the wave group, rather than “rays” or “radiation”, are the ones that can be matched to the job without guessing.

2. Microwaves are absorbed by water molecules in the soup [1]. The absorbed energy makes the water particles move faster, which raises the temperature [1]. The plastic contains little water and absorbs far less, so it stays cooler (it may warm a little because the soup heats it) [1]. [3] Examiner insight: Linking the absorber (water) to the heating is what turns a statement into an explanation.

3. (a) Sunburn or skin damage [1]; skin cancer (or premature skin ageing, or eye damage) [1]. [2] (b) Using sunscreen or covering the skin [1]; wearing sunglasses, or staying in shade, or limiting time at midday [1]. [2] Examiner insight: Two distinct hazards or measures are needed when two are asked for, because a repeated idea in different words is the same point.

4. X-rays are ionising and can damage cells and DNA, which can cause cancer [1]. The radiographer is exposed many times a day, so small doses add up to a large total [1]. The patient has one short exposure and gains a benefit (a diagnosis), so the risk is judged acceptable [1]. [3] Examiner insight: Strong answers compare total exposure with benefit, rather than simply saying “X-rays are dangerous”.

5. (a) Gamma rays are ionising and damage the cells they pass through [1]. A high dose can kill the cancer cells [1]. [2] (b) Each beam passes through different healthy tissue [1], but the beams all meet at the tumour, which gets a high dose while healthy tissue gets a lower dose [1]. [2] (c) Staff would be exposed repeatedly, so their total dose would build up [1]. [1] Examiner insight: An answer to (b) gains credit when it says where the beams overlap and where they do not.

6. Alternating current in the transmitter circuit makes electrons in the transmitting aerial oscillate [1]. The oscillating electrons give out radio waves of the same frequency [1]. The radio waves make electrons in the receiving aerial oscillate [1], producing an alternating current of the same frequency, which the radio circuit turns into sound [1]. [4] Examiner insight: Describing both ends of the link, with the aerial and the circuit named, is what the question asks for.

7. (a) Gamma rays penetrate the packaging to reach the gloves [1]. They kill microorganisms without heating the gloves [1]. [2] (b) Gamma rays are ionising and could harm staff [1]. Thick shielding absorbs them and no staff are present, so no one receives a dose [1]. [2] Examiner insight: Explaining the hazard before the protection tends to earn the marks in order.

8. X-rays pass through the wrist onto a detector [1]. Bone absorbs more X-rays than soft tissue, so fewer reach the detector behind bone and it shows as a pale area [1]. A break lets more X-rays through than solid bone [1], which gives a dark line across the pale bone [1]. [4] Examiner insight: Comparing the amounts absorbed in bone, soft tissue and the gap is the core of the explanation.

9. (a) The probe sends pulses of ultrasound into the body [1]. Part of each pulse is reflected at boundaries between different tissues [1]. The time for each echo to return shows how deep the boundary is, and the echoes are combined into an image [1]. [3] (b) The gel removes air between probe and skin, which would reflect most of the ultrasound at the skin [1]. [1] (c) Ultrasound is non-ionising, so it does not damage the cells or DNA of the baby [1], but X-rays are ionising, so they carry a risk of cancer [1]. [2] Examiner insight: Naming ultrasound as non-ionising and X-rays as ionising is the contrast that completes part (c).

10. (a) Round trip distance = speed × time = 1500 × 48 × 10⁻⁶ = 0.072 m [1]. Depth = 0.072 ÷ 2 = 0.036 m, which is 3.6 cm [1]. [2] (b) 1500 × 132 × 10⁻⁶ = 0.198 m [1]. Depth = 0.198 ÷ 2 = 0.099 m, which is 9.9 cm [1]. [2] (c) 9.9 − 3.6 = 6.3 cm [1]. [1] Examiner insight: Halving the distance for the there-and-back trip, and converting microseconds to seconds, are the two places most solutions go wrong.

11. (a) The skin emits infrared [1], and inflamed skin is warmer, so it emits more infrared than its surroundings and shows as a different area on the image [1]. [2] (b) Skin and tissue absorb infrared, so it does not penetrate to the bone [1]. The camera therefore only detects the surface and shows nothing about structures inside [1]. [2] Examiner insight: Separating “emitted from the surface” from “passes through the body” is what makes the contrast clear.

12. (a) Ultrasound [1]. Echoes from the baby show its position [1], and it is non-ionising so it is safe for the baby [1]. [3] (b) X-ray [1]. Bone absorbs more X-rays than soft tissue, so the bone shows up and a break is visible [1]. A short exposure keeps the dose low [1]. [3] (c) A gamma tracer [1]. The tracer emits gamma rays that pass out of the body and are detected outside, showing where it collects and how the organ works [1]. [2] Examiner insight: A method alone earns little here. The reason has to come from absorption, reflection or emission in that particular case.

Where marks are usually lost

• Writing “radiation” or “rays” instead of naming the wave group.
• Giving uses with no reason when the question asks you to explain.
• Writing “burn” for X-rays and gamma rays without mentioning cell or DNA damage and cancer.
• Saying bones “stop” X-rays, when they absorb more than soft tissue does.
• Saying ultrasound is an electromagnetic wave.
• Using the there-and-back distance as the depth.
• Leaving microseconds unconverted in the calculation, or forgetting the unit on the answer.
• Mixing up the roles of transmitting and receiving aerials.

Next steps

• Revise with the revision notes and re-read the study guide.
• Go to the OCR GCSE Physics hub and tick off the checklist.
• Take one of the free 10-minute diagnostics.
• Book a free trial class at /trial/.

Official syllabus

OCR, GCSE (9-1) Gateway Science Physics A (J249) specification, Version 5.0, July 2026, first assessment 2018. Section P5.2 The electromagnetic spectrum, statements P5.2g to P5.2j.