Calculadora de Atividade Radioativa
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
A = λ·N = (ln2/t½)·N
About this calculator
The Radioactive Activity Calculator determines the disintegration rate of a radioactive sample, measured in becquerels (Bq) or curies (Ci). It uses the formula A = λ·N, where λ is the decay constant (ln2 divided by half-life) and N is the number of radioactive atoms present. The calculation is essential for understanding the intensity of radiation emitted by a source.
To use the tool, enter the half-life of the isotope (in seconds, minutes, hours, days, or years) and the amount of material (mass in grams or number of atoms). The calculator automatically converts units and displays activity in Bq and Ci. For example, for Cobalt-60 (half-life 5.27 years), with 1 gram, the activity is approximately 1.13 × 10^13 Bq.
This calculator is useful in areas such as nuclear medicine (radiopharmaceutical dosing), radiological protection (risk assessment), carbon-14 dating, and scientific research. It also aids in planning the disposal of radioactive waste and environmental monitoring. Knowing the activity allows calculation of exposure doses and shielding requirements.
Important precautions: the formula assumes the sample is pure and decay follows an exponential law. Ensure you use the correct half-life for the isotope, as wrong values lead to inaccurate results. The calculated activity is instantaneous; for long periods, consider decay over time. Also, the mass must be of the specific isotope, not the chemical compound.
Frequently asked questions
What is radioactive activity and how is it measured?
Radioactive activity is the number of disintegrations per second of a sample. The SI unit is the becquerel (Bq), which equals one disintegration per second. The curie (Ci) is also used, where 1 Ci = 3.7 × 10^10 Bq.
How does half-life influence the activity calculation?
Half-life determines the decay constant λ = ln2 / t½. The shorter the half-life, the larger the constant and thus the higher the activity for the same number of atoms.
Can I use this calculator for any radioactive isotope?
Yes, as long as you provide the correct half-life and amount of material. The calculator works for any isotope that decays exponentially.
Is the result valid for an impure sample?
No, the formula assumes all atoms are the radioactive isotope in question. If the sample contains impurities or other isotopes, the actual activity may differ.
What is the difference between activity and radiation dose?
Activity is the disintegration rate of the source. Dose is the energy absorbed by a material or tissue due to radiation. Dose depends on activity, distance, exposure time, and radiation type.