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The radioactive decay of Cesium-137 sample

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1. Following a terrorist release of Cesium-137 (half-life of 30 years) in downtown, clean up efforts were successful in removing all but 100 curies. How long will it take for the contamination to decay to about 5 curies?

A. 90 years
B. 130 years
C. 175 Years
D. 215 years

please explain

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Hello and thank you for posting your question to brainmass.

Every 30 years the amount of CS-137 drops by a factor of two.

If we start with N0 nuclei, then after 30 years we will have N0/2 ...

Solution Summary

The solution shows how to obtain the time needed for the radiation to fall to a certain level.