Activity of a Radioactive Source Calculator
⚛ Modern physics. Use the Activity of a radioactive source formula to find activity, decay constant λ, number of nuclei: pick the value you want, type the others, and the answer updates as you go.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Activity | Bq |
| Decay constant λ | 1/s |
| Number of nuclei | no unit |
Worked example
Find the activity when Decay constant λ = 1.155 × 10⁻⁴ 1/s, Number of nuclei = 1 × 10⁷.
Using A = λ N: Activity = 1155 Bq.
Frequently asked questions
What is the formula for Activity of a radioactive source?
A = λ N.
What do the letters stand for, and what units are used?
Activity in Bq, Decay constant λ in 1/s, Number of nuclei.
How do you calculate activity?
Put the values into A = λ N. For example, with Decay constant λ = 1.155 × 10⁻⁴ 1/s, Number of nuclei = 1 × 10⁷, activity = 1155 Bq.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (activity, decay constant λ, number of nuclei) and fill in the others: it rearranges the formula for you.
