A radioactive isotope has a half-life of 90 minutes90\text{ minutes}90 minutes. It emits radiation at a rate of 160 particles per second160\text{ particles per second}160 particles per second. How long does it take for the rate of emission to fall to 20 particles per second20\text{ particles per second}20 particles per second?
90 minutes90\text{ minutes}90 minutes
180 minutes180\text{ minutes}180 minutes
270 minutes270\text{ minutes}270 minutes
360 minutes360\text{ minutes}360 minutes
144 exam-style questions on CIE IGCSE Physics 5.2.4a Half-life. Each one has a worked solution and a mark scheme showing where the marks go.