PH-691
Background radiation
Physics · Secondary 3 · Hard · Background radiation
In a lab, a Geiger–Müller tube records 18 counts in 2 minutes when no radioactive source is present. With a source placed nearby, it records 90 counts in 2 minutes. What is the count rate due to the source only?
- 9 counts per minute
- 36 counts per minute
- 45 counts per minute
- 72 counts per minute
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