IGCSE›Edexcel IGCSE Physics›Mind mapsRadioactivity, Uses & DangersEdexcel IGCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsBackgroundIonising radiation always presentEarth: rocks, radon, building materials, foodSpace: cosmic raysArtificial: medical X-rays, nuclear industryHalf-lifeActivity = decays per second, in becquerelsActivity always falls over timeHalf-life: time for activity to halveDifferent for each isotope800 Bq, 3 h half-life, 9 h → 100 BqUsesTracers diagnose conditions in the bodyRadiotherapy destroys tumour cellsBeta thickness gauges for paper and metalGamma sterilises food and equipmentAlpha source in smoke detectorsRadioactivityuses and dangersBqContaminationRadioactive material on or in the objectExposure continues until removed or decayedIrradiationExposure from an external sourceStops when source removed or you move awayExam tipsDo not swap contamination and irradiationState number of half-lives before halvingStore waste sealed and deep underground