A student measures the activity of a long-lived radioactive source using a Geiger-Müller counter. In a counting time of 5.0 minutes5.0\text{ minutes}5.0 minutes, the counter records 400 counts (corrected for background). Due to the random nature of radioactive decay, there is a statistical uncertainty associated with this count.
By what factor must the counting time be increased so that the percentage uncertainty in the count rate is reduced to exactly one-quarter of its original value?
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90 exam-style questions on OCR A A Level Physics Nuclear and particle physics, covering The nuclear atom, Fundamental particles, Radioactivity, and Nuclear fission and fusion. Each one has a worked solution and a mark scheme showing where the marks go.