# Calculating Activity of Iodine 123 After 24 Days

• JDiorio
In summary, a patient with thyroid problems has radioactive iodine 123 deposited in his thyroid gland. The initial activity of the iodine is 2.5 MBq and after 24 days, its activity should be 1.45E-7 Bq. However, there was an error in the calculation of the half-life of iodine 123, which should be 0.55 days instead of 13.1 hours. Using the correct half-life, the activity of the iodine after 24 days is 1.45E-7 Bq.
JDiorio

## Homework Statement

A patient with thyroid problems has radioactive iodine 123 deposited in his thyroid gland. If the iodine has an initial activity of 2.5 MBq, what is its activity after 24 days?

## Homework Equations

A(t)= Ao e^ -(ln(2)/half-life)*t

## The Attempt at a Solution

not sure what i did wrong here.. hope its not another calculating error.. but i found the half life of iodine 123 is 13.1 hours or .5458 days. So i have that ln(2)/.5458 times 24 = 30.48.
Then e^-30.48=5.795E-14.. i just multiply this number by 2.5E6 and get 1.45E-7 Bq.. not sure what I am doing wrong

1.45E-7 Bq is right, but are you sure the question says 24 days and not 24 hours? A thyroid scan is usually done 24 hours after the patient ingests a pill containing iodine-123, or 30 minutes after iodine is intravenously injected.

yeah i copied this directly from my homework site.. hmm.. its telling me that it is the wrong answer.. not sure what to do.. but it definitely says 24 days..

so is this answer correct?? because when i typed it in .. it said it wasn't..

I don't want to keep bumping this thread.. but i really need to know what I am suppose to do.. i have one more attempt at this problem on my homework site and i need all the points i can get.. I just need to know what is wrong with this answer

have you tried the answer for 24 hours?

I just found out that ur I123 half-life was wrong b/c I was working on the same HW. Try using 0.55day as the half-life, and you will get the correct answer!

cynthiayyf said:
I just found out that ur I123 half-life was wrong b/c I was working on the same HW. Try using 0.55day as the half-life, and you will get the correct answer!

THANK YOU! yeah i just did it with that number. So stupid. I use 13.2 hrs and it was 13.1. thanks a lot.

## 1. How do you calculate the activity of Iodine 123 after 24 days?

To calculate the activity of Iodine 123 after 24 days, you will need to use the equation A=A0*e^(-λt) where A is the current activity, A0 is the initial activity, λ is the decay constant, and t is the time in days. Plug in the values for A0 (initial activity) and t (24 days) and solve for A (current activity).

## 2. What is the decay constant of Iodine 123?

The decay constant of Iodine 123 is 0.0593 days^-1. This value can vary slightly depending on the source material and experimental conditions, but this is the most commonly used value for calculations.

## 3. Can the activity of Iodine 123 be calculated after a different time period?

Yes, the activity of Iodine 123 can be calculated after any time period using the same equation A=A0*e^(-λt). Simply plug in the values for A0 (initial activity) and t (time period) and solve for A (current activity).

## 4. How accurate are the calculated values for the activity of Iodine 123?

The calculated values for the activity of Iodine 123 are generally accurate, but they can vary slightly depending on the experimental conditions and the accuracy of the initial measurement of A0. It is important to use precise and accurate measurements for A0 and t in order to get the most accurate calculation for A.

## 5. What is the significance of calculating the activity of Iodine 123 after 24 days?

Calculating the activity of Iodine 123 after 24 days is important in understanding the rate of decay of this radioactive isotope. This information can be used in various scientific and medical applications, such as in nuclear medicine imaging and radiation therapy treatments. It also helps in monitoring and predicting the radioactive decay of Iodine 123 in various environments.

• Introductory Physics Homework Help
Replies
5
Views
2K
• Introductory Physics Homework Help
Replies
11
Views
4K
• Introductory Physics Homework Help
Replies
1
Views
2K
• Introductory Physics Homework Help
Replies
2
Views
1K
• Introductory Physics Homework Help
Replies
7
Views
1K
• Introductory Physics Homework Help
Replies
1
Views
904
• Introductory Physics Homework Help
Replies
7
Views
5K
• Introductory Physics Homework Help
Replies
6
Views
1K
• Introductory Physics Homework Help
Replies
24
Views
2K
• Introductory Physics Homework Help
Replies
2
Views
1K