Half-life

What the syllabus asks of you

• Define the half-life of a particular isotope as 2 Calculate half-life from data or decay curves the time taken for half the nuclei of that isotope from which background radiation has not been in any sample to decay; recall and use this subtracted definition in simple calculations, which might involve information in tables or decay curves (calculations will not include background radiation) 3 Explain how the type of radiation emitted and the half-life of an isotope determine which isotope is used for applications including: (a) household fire (smoke) alarms (b) irradiating food to kill bacteria (c) sterilisation of equipment using gamma rays (d) measuring and controlling thicknesses of materials with the choice of radiations used linked to penetration and absorption (e) diagnosis and treatment of cancer using gamma rays