Calculating Radioactivity: 4000 cpm to bq

[dagg3r]

a radioactive with a half-life of 5 days, has an initial activity of 4000 counts/min

determine the activity after 10 days

well because 1 half life is 5 days, so 10 days must be 2
so 4000/(2^2)
=1000 counts/min is that right?

2. If the initial quantitiy of radioactive material is 200gms determine the amount left after 15 days have elapsed
no of half lives = 3
200/(2^3)
=25 gms is that right?

3. convert 4000 counts per min into bq's
how do i do that?

 

[quantumdude]

Originally posted by dagg3r
a radioactive with a half-life of 5 days, has an initial activity of 4000 counts/min

determine the activity after 10 days

well because 1 half life is 5 days, so 10 days must be 2
so 4000/(2^2)
=1000 counts/min is that right?

Yes.

2. If the initial quantitiy of radioactive material is 200gms determine the amount left after 15 days have elapsed
no of half lives = 3
200/(2^3)
=25 gms is that right?

Yes.

3. convert 4000 counts per min into bq's
how do i do that?

You do it by looking up the definition of a bq in your book.

 

[M98Ranger]

1. Yes, your calculation for the activity after 10 days is correct. The activity would decrease by half after each half-life, so after 2 half-lives (10 days), the activity would be 1000 counts/min.

2. Your calculation for the amount of material left after 15 days is also correct. Each half-life, the amount of material would decrease by half, so after 3 half-lives (15 days), the amount left would be 25 gms.

3. To convert from counts per min to bq, you would need to know the conversion factor for the specific radioactive material you are working with. This conversion factor is based on the specific activity of the material and is typically given in bq per count. Without this information, it is not possible to accurately convert counts per min to bq.