lodine-125( is used to treat, among other things, brain rs and prostate cancer.

Question

lodine-125( is used to treat, among other things, brain rs and prostate cancer. It decays by gamma decay with a half-life of 54.90 days. Patients who fly soon after rig5 implants are given medical statements from the hospital verifying such treatment because their radiation could set o radiation detectors at airports. If the initial decay rate (or activity) was 527 Ci, what will the rate be after 361.0 days? Number uCi How many months after the treatment will the decay rate be reduced to 17.5% of the original value? Assume months of 30 days. Number months

Explanation / Answer

Here,

half life , T = 54.90 days

for the activity after 527 uCi

final activity = Ao * (0.50)^(t/T)

final activity = 527 * (0.50)^(361/54.90)

final activity = 5.53 uCi

the final activity is 5.53 uCi

===============================

for activity of 17.5 percent

final activity = Ao * (0.50)^(t/T)

0.175 = (0.50)^(t/54.90)

solving for t

t = 138 days = 4.6 months

the time taken is 4.6 months

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