Pick what to calculate — Remaining Quantity, Half-Life, Time Elapsed, or Initial Quantity — then fill in known values like N₀, N, and your Half-Life or Time Unit to get results alongside Decay Constant (λ), Mean Lifetime (τ), and Percentage Remaining/Decayed.
Calculated Result
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Decay Constant (λ)
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Mean Lifetime (τ)
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Percentage Remaining
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Percentage Decayed
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Radioactive decay is the process by which an unstable atomic nucleus loses energy by radiation. During this process, the nucleus transforms into a more stable configuration, emitting particles or electromagnetic radiation.
Half-life is the time required for exactly half of a radioactive substance to decay. It's a constant characteristic of each radioactive isotope and can range from fractions of a second to billions of years.
The decay constant (λ) is calculated using the formula λ = ln(2) / t₁/₂, where ln(2) ≈ 0.693 and t₁/₂ is the half-life. The decay constant represents the probability of decay per unit time.
Mean lifetime (τ) is the average time a nucleus will exist before decaying. It's related to half-life by τ = t₁/₂ / ln(2) ≈ 1.44 × t₁/₂. Mean lifetime is always longer than half-life.
Carbon-14 dating uses the known half-life of carbon-14 (5,730 years) to determine the age of organic materials. By measuring the remaining C-14 in a sample and applying decay formulas, scientists can calculate when the organism died.
Accuracy depends on precise measurements of initial and remaining quantities, accurate knowledge of the half-life constant, and ensuring no external contamination. Environmental factors generally don't affect nuclear decay rates.
Short half-lives indicate rapid energy release through radiation, creating higher radiation doses in shorter periods. Long half-lives release energy slowly over extended periods, resulting in lower immediate radiation exposure rates.