An experimental physicist is measuring the activity of a radioactive sample in a laboratory with a constant background count rate of 45 s-1. Initially, the Geiger-Müller counter registers a total count rate of 365 s-1. The radioisotope in the sample has a half-life of 6.0 hours6.0\text{ hours}6.0 hours.
What total count rate will the Geiger-Müller counter register after a period of 18.0 hours18.0\text{ hours}18.0 hours?
40 s−140\text{ s}^{-1}40 s−1
46 s−146\text{ s}^{-1}46 s−1
85 s−185\text{ s}^{-1}85 s−1
125 s−1125\text{ s}^{-1}125 s−1
41 exam-style questions on OCR GCSE Physics Radioactive emissions. Each one has a worked solution and a mark scheme showing where the marks go.