Pearson Edexcel · GCSE · Physics
Course version: 1PH0 · Version from Sept 2016
6.30P Explain how the dangers of ionising radiation depend on half- life…
Full specification wording
Topic 6 – Radioactivity: 6.30P Explain how the dangers of ionising radiation depend on half- life and relate this to the precautions needed
Half-life is the time for half the unstable nuclei in a sample to decay, so it sets how long a source stays significantly radioactive.
Checked against the Pearson Edexcel 1PH0 specification (opens in a new tab) on .
- Point 29 of 42
Study notes
From the checked teaching notes for this specification point.
The idea
Half-life is the time for half the unstable nuclei in a sample to decay, so it sets how long a source stays significantly radioactive. A short half-life means the activity falls quickly, so the source is intensely radioactive for a short period and then becomes much safer; a long half-life means the activity persists for a very long time, so the hazard remains for years. Precautions must match this: a short-half-life source needs strict handling while it is active but can be stored until it decays; a long-half-life source needs permanent shielding, secure long-term storage and careful disposal because the danger will not fade quickly.
What earns the marks
- States that a short half-life means activity falls quickly, so the source is dangerous only for a short time.
- States that a long half-life means the source stays radioactive for a long time, so the hazard persists.
- Links a long half-life to long-term precautions such as permanent shielding, secure storage or careful disposal.
- Links a short half-life to precautions such as strict handling while active and storage until activity decays.
- Rejects an option that reverses the relationship between half-life length and how long the danger lasts.
Common mistakes and how to put them right
Reverses the relationship; state that a long half-life means the danger lasts longer, not shorter.
Treats half-life as irrelevant to safety.
Put it right: Explain that it determines how long precautions must be maintained.
Assumes a short half-life removes all risk immediately.
Put it right: Recognise the source is still intensely active for a short period and needs handling then.
Exam tips
- Check whether the option keeps the direction right: longer half-life means longer-lasting hazard.
- Match the precaution to the timescale, choosing long-term storage for long half-lives and short-term handling for short half-lives.
- Eliminate options that claim half-life has no effect on the precautions needed.
Try the lesson
The start of the Topic 6 – Radioactivity: 6.30P Explain how the dangers of ionising radiation depend on half- life and relate this to the precautions needed lesson, made from checked teaching notes for this specification point.
Have a go first
Why is a source with a long half-life often more hazardous to store than one with a short half-life?
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