AQA · Physics · 8463
GCSE Physics: Different half-lives of radioactive isotopes
Atomic structure · AQA GCSE Physics (8463), specification point 4.4.3.2. Cards are generated from the exam board's own specification for "Different half-lives of radioactive isotopes", and every card links back to the page it came from. Separate science only. Specification © AQA — used with attribution.
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How much do the half-lives of different radioactive isotopes vary?
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Over a very wide range — from fractions of a second to billions of years.
Why is an isotope with a short half-life an intense hazard at first?
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Its activity is high — many decays per second — so it emits a lot of radiation initially, although this dies away quickly.
Why is an isotope with a long half-life hazardous for a long time?
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Its activity is low, but it keeps decaying for a very long time, so it remains radioactive (and contaminating) for years or centuries.
How does half-life affect how quickly a source's activity falls?
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The shorter the half-life, the faster the activity falls — it halves every half-life.
A radioactive source with a ? half-life has a high initial activity that falls quickly.
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short
For the same number of nuclei, which has the higher activity: a short or a long half-life isotope?
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The short half-life isotope — its nuclei decay more often per second.
Why are half-life values often written in standard form?
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Because they span many orders of magnitude (e.g. 10⁻³ s to 10⁹ years), standard form keeps very large and very small values readable and comparable.
Write a half-life of 4,500,000,000 years in standard form.
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4.5 × 10⁹ years.
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