Background Radiation, Contamination & Irradiation — Atomic Structure | Physics with Kate

Topic 07

🔮 Background Radiation, Contamination & Irradiation 🔮

Understanding the radiation around us every day, and the critical difference between contamination and irradiation.

✦ Background Radiation

🎬

What Is It?

Background radiation is the low-level nuclear radiation that exists all around us, all the time. It comes from both natural and man-made sources. We must account for it in experiments by measuring it first and subtracting it from readings.

Source	Type	Average (µSv/year)
Radon gas (from rocks)	Natural	2.0
Cosmic radiation	Natural	0.3
Food and drink	Natural	0.2
Other natural sources	Natural	0.6
Medical X-rays	Man-made	0.4
Total		3.5

Biggest Source

Radon gas is the largest single contributor to background radiation. It seeps out of certain rocks (especially granite) and can accumulate in buildings. The level varies by location.

✦ Sources of Background Radiation

🩶 Background Radiation Sources — Pie Chart

Background radiation sources in the UK. Radon gas from rocks is by far the largest contributor, accounting for over half of the total dose.

🩺 ✦ 🩺 ✦ 🩺

✦ Contamination vs Irradiation

🎬

☣️ Contamination

The unwanted presence of radioactive materials on or inside an object or person. The radioactive atoms are physically there and continue to emit radiation. Harder to deal with — you must remove or contain the material.

🛡️ Irradiation

Exposure to radiation from a source outside the object. The object does not become radioactive. Once the source is removed, the irradiation stops. Easier to deal with — just move away from the source.

🩶 Contamination vs Irradiation — Visual Comparison

Contamination means radioactive material is physically present on or in the object and continues to emit. Irradiation is exposure from an external source — the object itself stays clean.

✦ Safety Precautions

Handling Radioactive Sources

Wear gloves to prevent contamination of skin (radioactive material getting on you)
Use tongs to increase distance from source
Keep sources in lead-lined containers when not in use
Limit exposure time

🩶 Safety Precautions When Handling Sources

Four key safety precautions when handling radioactive sources: wear gloves, use tongs, store in lead-lined containers, and limit exposure time.

🩺 ✦ 🩺 ✦ 🩺

Question 1 [1 mark]

What is radioactive contamination?

A. Exposure of an object to nuclear radiation
B. The unwanted presence of materials containing radioactive isotopes on other materials
C. The decay of radioactive atoms
D. The process of cleaning radioactive materials

✦ Answer

B. Contamination is the unwanted presence of radioactive materials on (or in) other materials.

Question 2 [1 mark]

How does irradiation differ from contamination?

A. Irradiation causes objects to become radioactive
B. Contamination exposes objects to radiation
C. Irradiation exposes objects to radiation without making them radioactive
D. Contamination is a type of irradiation

✦ Answer

C. Irradiation is being exposed to radiation from an external source. The object does not become radioactive itself.

Question 3 [3 marks]

Orla carries out a demonstration with radioactive sources and wears plastic gloves. Explain why.

✦ Answer

To prevent radioactive contamination of her skin [1]. If radioactive material got on her skin it would continue to irradiate her cells at close range [1], which could cause cell damage or mutations even after the demonstration ends [1].

Question 4 [2 marks]

Name two natural sources and one man-made source of background radiation.

✦ Answer

Natural: radon gas from rocks, cosmic rays from space (also accept: food/drink, rocks/soil) [1 each].
Man-made: medical X-rays (also accept: nuclear fallout, nuclear power) [1].

Question 5 [2 marks]

A Geiger-Müller tube measures an average background radiation level of 0.3 counts per second. A radioactive sample is placed near the detector and the total reading is 8.3 counts per second. What is the radiation from the sample alone?

✦ Answer

8.3 − 0.3 = 8.0 counts per second [2]. You must subtract the background radiation to find the true count rate from the sample alone.

Question 6 [2 marks]

Using the data table above, calculate the total contribution of natural sources of background radiation.

✦ Answer

2.0 + 0.3 + 0.2 + 0.6 = 3.1 µSv/year [2]. (Cosmic + radon + food + other natural)

Question 7 [2 marks]

Explain why a doctor may recommend a medical X-ray despite the risks associated with nuclear radiation.

✦ Answer

The benefit of diagnosis (finding broken bones, tumours, etc.) outweighs the small risk from the low dose of radiation [1]. The radiation dose from a single X-ray is very small compared to annual background radiation [1].

Question 8 — Diagram Question [3 marks]

The diagram below shows the sources of background radiation in the UK. Use it to answer the following questions.

Pie chart showing the main sources of background radiation in the UK.

(a) Identify the largest single source of background radiation. [1]
(b) Calculate the total percentage contribution from natural sources. [1]
(c) Suggest why the level of background radiation might be higher in Cornwall than in London. [1]

✦ Answer

(a) Radon gas is the largest single source, at 57.1% [1].
(b) 57.1 + 17.1 + 8.6 + 5.7 = 88.5% from natural sources [1].
(c) Cornwall has more granite rock, which releases more radon gas [1]. This means the proportion from radon is higher there.

Question 9 — Diagram Question [3 marks]

A worker in a nuclear facility encounters two situations, shown in the diagram below. Study the diagram and answer the questions.

Two situations a nuclear worker might encounter. Identify which is contamination and which is irradiation.

(a) Which situation shows contamination? Explain your answer. [1]
(b) Which situation shows irradiation? Explain your answer. [1]
(c) State one action the worker should take in Situation A to reduce their risk. [1]

✦ Answer

(a) Situation A is contamination — the worker has radioactive material (dust) physically on their clothing, which will continue to emit radiation [1].
(b) Situation B is irradiation — the worker is being exposed to radiation from an external source. The worker themselves does not become radioactive [1].
(c) The worker should remove the contaminated clothing carefully and wash thoroughly to remove the radioactive material [1]. (Also accept: use decontamination shower, seal clothing in a bag for disposal.)

Question 10 [3 marks]

Explain why radioactive contamination is generally considered more dangerous than irradiation. Your answer should compare how each is dealt with and the risks involved.

✦ Answer

With contamination, the radioactive material is on or inside the body, so it continues to irradiate cells at very close range [1]. The source cannot simply be moved away — it must be physically removed or contained, which is much more difficult [1]. With irradiation, removing the external source or moving away immediately stops the exposure, whereas a contaminated person remains exposed until the material is removed or decays [1].

← Uses of Isotopes ↑ All Topics Next: Fission & Fusion →

A Level - February

PHYSICS ONLY

16, 17, 18, 19 Feb 2026

Revision Course

GCSE - Easter

BIOLOGY, CHEMISTRY PHYSICS

7 - 10 April 2026

Revision Course

Click to Bookonly 8 places left

A Level & GCSE

PHYSICS ONLY

Term - Time

one to one

How You Can Work With Me

Support is offered in clear layers, so students and families can choose what fits best.

Free Community Access

A welcoming starting point with BRIDGE-based resources and introductory courses.

1:1 Specialist A-level Physics Support

Personalised teaching rooted in deep understanding, confidence, and exam success.

Small Group Programmes

Structured learning with motivated peers, focused on thinking, discussion, and application.

About Kate

I’m Kate — an experienced Physics teacher, examiner, and the founder of Physics with Kate.

Over more than 15 years, I’ve taught and examined thousands of students and seen first-hand how capable girls can lose confidence in Physics at A-level. I’ve also seen how quickly that changes when teaching focuses on understanding, courage, and belonging.

The BRIDGE Framework grew from real classrooms, real results, and a deep belief that girls belong in Physics — and can excel in it.

Ready to Build Confidence in Physics?

Whether you’re looking for structured support, a specialist tutor, or a community that truly understands A-level Physics, you’re in the right place do join my community or book in with me to find out more about I can support you, your department or your child.

A Community Where Girls Belong in Physics

The Physics with Kate Community is a supportive, academically focused space for girls studying A-level Physics.

Inside the community, students have access to:

Free BRIDGE-based mini courses
- Brave and opened - Guided problem-solving sessions
- Real understanding of the concepts
- Insight by applying formulas and calculations to solve problems
- Demonstrate understanding with exam technique support and revision resources
- Growth, support with UCAS, extra-curricular competitions and projects and industry links
- Example Visible sixth formers normalise girls in Physics for younger year groups
Free to join a network of like-minded girls who take Physics seriously
Subscriptions for 1:1 and group tutoring

This is a place where curiosity is encouraged, ambition is normalised, and girls feel confident to ask questions and think deeply.

Kate is a gifted teacher who has always made physics interesting and fun. She is full of energy and so supportive. I highly recommend her. We owe her a massive thank you for helping our son brush up before he took Oxford's Physics Aptitude Test last year -- he just got an offer today!

Kitty

Mum

20-06-2025

"Thanks for you excellent tutoring with my daughter over the summer. Having struggled with physics over the last year in just a few sessions her confidence and interest in physics has 100% turned around and she is going into year 10 with a renewed interest”.

Salma

Mum

20-06-2025

My Son just finished the Science GCSE revision week with Kate, Chloe and Debs and came away feeling much more confident in all three Sciences. The excellent course structure, detailed knowledge and continual support provided over the past week has really helped him to focus and approach his Science GCSE with real optimism! I wouldn’t hesitate to recommend! Thank you again

Nick

Parent

15-04-2025

The GCSE science revision course exceeded our expectations in every way. Not only did my daughter grow in confidence and practice her exam technique, but she also enjoyed working in small groups and the warm, engaging style of all three teachers. Thank you for a brilliant course! — Kate

Kate

Parent

20-04-2025

Thankyou so much Kate. My daughter was really happy and said her chemistry teacher was the best teacher she had ever had…!She also loved the physics and knows she has to put some work into her biology.I really am grateful it is a great idea and really helped me focus on my work whilst I knew my daughter was focusing on revision. - Mum of a Year 11 Student

Mum

Parent

21-04-2025

Thank you so much! My daughter really enjoyed and got a lot out of the week - we’ve enjoyed her dinner time science lectures too! (this evenings was hierarchy of waves and parts of the heart.) Thanks also for accommodating her today - that worked really well for her. - Mum of a Year 11 Student

Mum

Parent

20-06-2025

... enjoy science more than ever. These tutoring sessions have greatly helped me to not only improve my knowledge and understanding of science, but have caused me to enjoy science more than ever. - Daniel, Dulwich

Daniel

GCSE Student

22-10-2024

Very helpful and enjoyable - Lucy, Dulwich

Lucy

GCSE Student

23-10-2024

Best teacher ever Best teacher ever helped my a level understanding of physics to the point where I think I have gotten an A in the exams. Teaches in detail and covers every aspect of the course. Best teacher ever!! - Milo, London

Milo

A Level Student

08-06-2024

Kate has been tutoring my niece A-level Physics, online (she lives Cornwall, so online was the best option for her). She does weekly sessions with her that are fully tailored to my niece’s requirements. She has been a great confidence booster, positive tutor and my niece’s confidence has skyrocketed. Kate goes through difficult topics, marks work and sets homework. I’m pleased to say that, because of Kate, my niece’s UCAS prediction has gone up 2 grades. I have nothing but positive comments to say about the difference Kate has made and I feel lucky to have found her as a tutor. What started off as a boring, Auntie Christmas present (a block of tutoring) has ended up being the best present ever!! - P Lamy

P Lamy

Parent

15-03-2024

Kate has been amazing! We couldn't be happier! Kate has been tutoring our daughter remotely in her final year of A level Physics. She has had such a positive impact on her confidence and enthusiasm across her other subjects too, showing a lot more focus since the sessions began. Kate has a great way of explaining/teaching in a very structured and approachable way. Our daughters grades have seen a huge improvement in a short time. It was important for us to find a tutor that our daughter could feel comfortable with. We honestly couldn't recommend Kate any higher, she's been great - Sarah

Sarah

Aunt

10-01-2024

Fabulous Physics tutoring I cannot recommend Kate highly enough. She was a brilliant teacher to my son when he was struggling with A’Level Physics. Her teaching style and organised plans to cover the topics both made it understandable to him and gave him new levels of confidence. She worked with him both in person and online and kept in contact making sure he was completing the work she set him. His A Level result which then gained him his place at Loughborough university was entirely down to her excellent work with him. A brilliant tutor! - Liz Pharaoh

Liz Pharaoh

Parent

05-05-2024