IGCSE›Oxford AQA IGCSE Physics›Mind mapsIonising Radiation from the NucleusOxford AQA IGCSE Physics: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsDecayRandom process, unpredictable per nucleusUnstable nucleus emits radiation to be stableMay form a different elementBackground radiation always present (rocks, cosmic rays, X-rays)Three typesAlpha: 2 protons + 2 neutrons, a helium nucleusBeta: fast electron from neutron → protonGamma: electromagnetic radiation from nucleusCompareAlpha: strongly ionising, stopped by paperBeta: moderately ionising, stopped by mm of aluminiumGamma: weakly ionising, stopped by thick leadMore ionising → less penetratingRadiationfrom the nucleusαβγHalf-lifeTime for nuclei or count rate to halve800 counts/min, 5 day half-lifeAfter 15 days = 3 half-lives800 ÷ 2 ÷ 2 ÷ 2 = 100 counts/minHazardsContamination: unwanted radioactive atoms on a materialIrradiation: exposure without contactIrradiated object not radioactiveUse tongs, shielding, short time, distanceHazard depends on type and half-lifeExam tipsAlpha strong ionising, weak penetrating; gamma the reverseNever say irradiated objects become radioactive