What you’ll learn3 learning objectivesChoose one objective for a focused lesson, or study the complete topic.5.2.4.1Half-life as the time for half the• Define half-life as the time for half the nuclei in any sample to decay; use it in simple calculations with tables or decay curves, excluding background radiationSyllabus objective5.2.4.2Half-life from data or decay curves• Calculate half-life from data or decay curves from which background radiation has not been subtractedSyllabus objective5.2.4.3Isotope choice using radiation type• Explain isotope choice using radiation type and half-life for: (a) smoke alarms (b) food irradiation (c) gamma sterilisation of equipment (d) material thickness control linked to penetration/absorption (e) cancer diagnosis/treatment using gamma raysSyllabus objective