It is assumed that level of carbon-14 in the atmosphere is constant.
The best-known radiometric dating techniques include radiocarbon dating, potassium-argon dating, and uranium-lead dating.
Therefore, the half-life of a radioactive element is independent of the amount of sample.
With the help of half-life values of a suitable radioisotope of an element, which is present in a rock, or in an artifact, the age of the rock and the artifact can be determined.
By establishing geological timescales, radiometric dating provides a significant source of information about the ages of fossils and rates of evolutionary change, and it is also used to date archaeological materials, including ancient artifacts.
The different methods of radiometric dating are accurate over different timescales, and they are useful for different materials.