1) A sample of cesium-137 has an activity of 4.00 µCi and a half-life of 30.2 ye
ID: 2075638 • Letter: 1
Question
1) A sample of cesium-137 has an activity of 4.00 µCi and a half-life of 30.2 years. How many cesium-137 nuclei are present in the original sample?
Correct, computer gets: 2.03e+14
2) The sample of cesium-137 emits gamma rays that have an energy of 684 keV each. Assume that you enclose the entire sample in your hand and that your hand represents 0.780 kg of tissue. If your hand absorbs 22% of the radiation emitted, calculate the equivalent dose absorbed by your hand tissue if you hold the cesium-137 sample for 13 minutes. (Compare your answer with the average dose your whole body receives in a year due to natural events, which is around 300 mrem.)
Explanation / Answer
1)
acitvity , A = 4 uCi
A = 4 * 3.7 *10^10 Bq
let the number of nuclei is N
activity = lamda * N
4 * 3.7 *10^10 = ln(2)/(30.2 * 365 * 24 * 3600) * N
solving for N
N = 2.03 *10^14
the number of nuclei is 2.03 *10^14
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please post the other question in a seperate post
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