How can the concept of half-life be used to determine the age of a substance?

The concept of half-life can be used to determine the age of a substance by measuring the amount of a radioactive isotope present and comparing it to its stable decay products. By knowing the half-life of the isotope, which is the time it takes for half of the original substance to decay, scientists can calculate how many half-lives have passed since the substance was formed. This allows them to estimate the age of the material, commonly used in techniques like radiocarbon dating for organic materials.