A small gamma source gives 400 counts per minute at 1.0 m. Ignoring background and absorption, what is the rate at 2.0 m?
Answer and explanation
Correct answer: C. 100 counts per minute
- Step 1: Intensity follows the inverse square law. Step 2. Doubling the distance divides the rate by . Answer: 100 counts per minute. Why not the others: 200 would be the inverse-proportional result; 50 would be a factor of 8; 25 would be a factor of 16.
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