A Geiger-Muller tube and counter detect radiation, clicking once for each bit of radiation that reaches it. Even with no source nearby it keeps clicking slowly, because background radiation is all around us, from rocks, the air, space and our food. To find the count rate from a source alone, you must subtract this background. Move the source to hit the target count rate.
MissionPlace the source so its count rate (after subtracting background) is 100 counts/min.Round 1Streak 0Best 0
Compared with the target, the source count rate is:
The counter is already ticking on background radiation. Set the distance, predict, then take the reading.
background count rate22 / min
measured count rate (with source)?
corrected = measured - background?
The corrected count rate is the count rate due to the source alone.