Question

4.Strontium-90 has a half-life of 28.8 years. How long will it take for a 5-count sample to decay to 0.3125 counts?


5. Germanium-66 has a half-life of 2.5 hours. After 10 hours, only 25 counts of an original sample are emitted, what was the radiation of the original sample?


6.The half-life of carbon-14 is 5730 years. If a sample of wood containing 60 counts of carbon-14 when alive now only emits 3.75 counts, how old is the sample?

Answer 1

Answer:

115

Explanation:

0.3125 / 5 = 0.0625 (this is the decimal percent remaining)

(1/2)^n = 0.0625

n log o.5 = log 0.0625

n = 4

(Alternate: you know by experien ce that )1/2)^4 = 1/16 = 0.0625)

28.8 times 4 = 115.2 yr