Radioactive iodine-131 has a half-life of eight days.If a dose with an activity of 200uCi is given to a patient today,how much of the radioactivity will...

Question

Radioactive iodine-131 has a half-life of eight days. If a dose with an activity of 200uCi is given to a patient today, about how much of the radioactivity will still remain active after 32 days?    do it with steps please

Answer 1

Recall that a half life is defined as the time required for one-half of a radioactive sample to decay.  

The problem states that for I-131 it is 8 days.  

So every 8 days, the sample is smaller by half and so is the activity.  

Since 32 days equals 4 half-lives, the size of the sample (and the activity) will be halved 4 times.  

 

You might sketch it out like this, starting from 200 uCI

 

200 uCi  --------> 100 uCi  ---------> 50 uCi ----------> 25 uCi ---------> 12.5 uCi

 

where every arrow indicates 8 days, so after 32 days, only 12.5 uCi activity remains