The reading on a detector placed near a radioactive material is 740 counts per second740\text{ counts per second}740 counts per second. The background count rate is 60 counts per second60\text{ counts per second}60 counts per second. The half-life of the radioactive material is 15 days15\text{ days}15 days. What is the reading on the detector after 45 days45\text{ days}45 days?
85 counts per second85\text{ counts per second}85 counts per second
93 counts per second93\text{ counts per second}93 counts per second
145 counts per second145\text{ counts per second}145 counts per second
230 counts per second230\text{ counts per second}230 counts per second
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.