Background radiation.pptx

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Background radiation

Atomic structure

Lesson 8 of 10

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Warm-up

Atomic structure

Lesson 8 of 10

Answer each one, then check.

1

What is radiation?

2

Name a rock that contains radioactive material.

3

What does mSv stand for?

4

Where do cosmic rays come from?

5

What is a Geiger-Müller tube?

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Warm-up - Answers

Atomic structure

Lesson 8 of 10

1

What is radiation?

Energy emitted as waves or particles

2

Name a rock that contains radioactive material.

Granite

3

What does mSv stand for?

Millisievert

4

Where do cosmic rays come from?

Space

5

What is a Geiger-Müller tube?

A detector of radiation

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Learning Objectives

Atomic structure

Lesson 8 of 10

1

Describe the sources of background radiation.

2

Explain why radiation dose varies with location and occupation.

3

Use data on radiation dose in millisieverts.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Atomic structure

Lesson 8 of 10

BACKGROUND RADIATION

Background radiation is around us all of the time. It comes from natural sources such as rocks and cosmic rays and from man-made sources such as fallout from nuclear weapon tests and accidents.

Radiation dose is measured in sieverts (Sv). 1000 millisieverts (mSv) = 1 sievert. You do not need to recall the unit.

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Sources of Background Radiation

Atomic structure

Lesson 8 of 10

Most background radiation is natural.

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Where Does It Come From?

Atomic structure

Lesson 8 of 10

Natural: rocks

Radioactive isotopes in rocks such as granite release radon gas.

Natural: cosmic rays

High-energy particles from space; stronger at altitude.

Natural: food and air

Small amounts in food, drink and the air.

Man-made

Fallout from nuclear weapon testing and accidents, and medical procedures.

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Why Dose Varies

Atomic structure

Lesson 8 of 10

Location and occupation.

Factor

Effect

Location

Areas with granite rock have higher radon levels; high altitudes have more cosmic rays.

Occupation

Airline crews (cosmic rays), radiographers and nuclear workers receive higher doses.

Medical treatments

X-rays and scans add to a person's dose.

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Using a Pie Chart

Atomic structure

Lesson 8 of 10

The typical annual dose is 2.7 mSv. Radon is 50% of this. Calculate the dose from radon.

1

Fraction

50% = 0.50

2

Multiply

0.50 × 2.7

3

Answer

1.35 mSv

ANSWER

1.35 mSv (about 1.4 mSv)

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Converting Units

Atomic structure

Lesson 8 of 10

Convert 2.7 mSv to sieverts.

1

1000 mSv = 1 Sv

2.7 ÷ 1000

2

Answer

0.0027 Sv (2.7 × 10⁻³ Sv)

ANSWER

2.7 × 10⁻³ Sv

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Measuring It

Atomic structure

Lesson 8 of 10

How background is found.

Detector

A Geiger-Müller tube and counter measures the count rate.

Correct

Subtract the background count rate from measurements on a source.

Vary

Background changes with place and time, so measure it in the same place.

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Key Terms

Atomic structure

Lesson 8 of 10

Background radiation

Radiation that is around us all the time.

Cosmic rays

High-energy particles from space.

Radon

A radioactive gas from rocks.

Radiation dose

A measure of the risk of harm from radiation, in sieverts.

Millisievert

One thousandth of a sievert.

Man-made

Produced by human activity.

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Atomic structure

Lesson 8 of 10

YOUR TASK

Why Does It Differ?

10 minutes

Explain why the background radiation is higher in Cornwall (granite) than in London, and why an airline pilot receives a higher dose than an office worker.

1

Name the source.

2

Link it to location or job.

WHAT A GOOD ANSWER SHOWS

Granite rocks contain radioactive isotopes and release radon gas, so background is higher. Pilots fly at high altitude where there are more cosmic rays.

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Can I...?

Atomic structure

Lesson 8 of 10

List natural sources.

List man-made sources.

Explain location effects.

Explain occupation effects.

Use a pie chart.

Convert mSv to Sv.

Correct for background.

Explain why background varies.

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Summary & Exam Focus

Natural: rocks, cosmic rays, food.

Man-made: fallout, medical procedures.

Dose varies with location and occupation.

1000 mSv = 1 Sv.

EXAM FOCUS

Give two natural sources of background radiation. (2 marks)

Any two: rocks, cosmic rays, food.

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