Half-lives hazards and uses of nuclear radiation.pptx

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Half-lives, hazards and uses of nuclear radiation

Atomic structure

Lesson 9 of 10

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up

Atomic structure

Lesson 9 of 10

Answer each one, then check.

1

What is half-life?

2

What is a tracer?

3

Which radiation is most penetrating?

4

Give one danger of ionising radiation.

5

What is standard form?

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up - Answers

Atomic structure

Lesson 9 of 10

1

What is half-life?

The time for activity to halve

2

What is a tracer?

A substance that can be followed inside the body

3

Which radiation is most penetrating?

Gamma

4

Give one danger of ionising radiation.

It can damage or kill cells

5

What is standard form?

A number written as a × 10ⁿ

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Learning Objectives

Atomic structure

Lesson 9 of 10

1

Explain why the hazards of a radioactive material differ with its half-life.

2

Describe and evaluate the use of nuclear radiation in exploring internal organs and treating unwanted tissue.

3

Evaluate the perceived risks of nuclear radiation using data.

4

Use data given in standard form.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Atomic structure

Lesson 9 of 10

HALF-LIFE AND HAZARD

Radioactive isotopes have a very wide range of half-lives. Short half-lives are very active but decay quickly; long half-lives stay radioactive for a very long time.

In medicine, nuclear radiations are used to explore internal organs and to control or destroy unwanted tissue.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Nuclear Radiation in Medicine

Atomic structure

Lesson 9 of 10

The radiation is chosen for its penetration and half-life.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Half-Life and Hazard

Atomic structure

Lesson 9 of 10

Data (approximate).

Isotope

Half-life

Comment

Technetium-99m

6 hours

Gamma emitter used as a medical tracer; gone from the body quickly

Iodine-131

8 days

Used to treat the thyroid; decays within weeks

Cobalt-60

5 years

Gamma source for radiotherapy

Uranium-238

4.5 × 10⁹ years

Stays radioactive for billions of years

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Why Half-Life Matters

Atomic structure

Lesson 9 of 10

Explain why a source with a very long half-life is a hazard for a long time, and why a source with a very short half-life is a hazard mainly at first.

1

Very long half-life

The activity falls extremely slowly, so it remains radioactive for a very long time

2

Very short half-life

It is very active at first but decays quickly, so it is a hazard for only a short time

ANSWER

Long half-life: long-term hazard, low activity. Short half-life: intense at first but soon gone.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Choosing a Medical Tracer

Atomic structure

Lesson 9 of 10

Explain why technetium-99m is suitable as a tracer to explore organs in the body.

1

Gamma

Penetrating, so it passes out of the body to the detector, and weakly ionising, so it does little damage

2

Half-life 6 hours

Long enough to take the scan but decays quickly so the patient is not radioactive for long

ANSWER

It emits gamma rays, which pass out of the body and are weakly ionising, and its half-life is short.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Evaluating Risk

Atomic structure

Lesson 9 of 10

Balance benefits and risks.

Benefits

Diagnose disease without surgery; destroy tumours.

Risks

Ionising radiation can damage healthy cells and cause cancer.

Reduce risk

Use small doses, short half-lives and beams from different directions.

Judging

Use the data on dose and consequences to say whether the risk is acceptable.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Key Terms

Atomic structure

Lesson 9 of 10

Tracer

A radioactive substance used to follow a process in the body.

Radiotherapy

Treating cancer using nuclear radiation.

Half-life

The time for the activity to halve.

Gamma camera

A device that detects gamma rays from a tracer.

Unwanted tissue

Tissue such as a tumour.

Risk

The chance of harm.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Atomic structure

Lesson 9 of 10

YOUR TASK

Evaluate the Scan

12 minutes

A doctor uses technetium-99m (half-life 6 hours, gamma) to scan a patient's kidneys. Give two reasons why it is suitable and one risk.

1

Consider penetration.

2

Consider half-life.

WHAT A GOOD ANSWER SHOWS

Reasons: gamma passes out of the body; short half-life. Risk: ionising radiation may damage cells (small).

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Can I...?

Atomic structure

Lesson 9 of 10

Explain hazard and half-life.

Explain why gamma tracers are used.

Explain why a short half-life suits a tracer.

Describe radiotherapy.

Explain beams from different directions.

Evaluate risks and benefits.

Read standard form data.

Use data in an answer.

openrevise.com

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Summary & Exam Focus

Half-lives range from fractions of a second to billions of years.

Tracers: gamma, short half-life.

Radiotherapy: focus beams to destroy tumours.

Weigh benefits and risks.

EXAM FOCUS

Explain why a radioactive tracer used inside the body should emit gamma radiation and have a short half-life. (4 marks)

Gamma passes out of the body and short half-life means it does not remain long.

openrevise.com