Key idea
Radioactive dating
t = ln(N₀/N)/λ = T½
Radiometric dating uses known radioactive decay laws and isotope ratios to infer elapsed time, provided the relevant system history and initial conditions are adequately constrained.
Radioactive dating
The key idea
Radiometric dating uses known radioactive decay laws and isotope ratios to infer elapsed time, provided the relevant system history and initial conditions are adequately constrained.
Why it matters
Different isotope systems suit different materials and timescales; dating is therefore a measurement model, not simply reading an age directly from a sample.
A picture to remember
Key idea
Radioactive dating
Guided example
Radioactive dating
Radiometric dating uses known radioactive decay laws and isotope ratios to infer elapsed time, provided the relevant system history and initial conditions are adequately constrained.
Put it into practice
Radioactive dating
Choose a concrete case linked to Radioactive dating. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.
Check your answer
A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.