Explain how the half-life of a radioactive isotope affects the usefulness of that isotpe in dating specific types of rock?

Answer 1

Half-lives vary widely: some radioisotopes will be reduced by half in less than a second whereas for others it takes billions of years. So different radioisotopes are best suited to dating rocks of various ages. For example, a scientist wouldn't use a parent isotope with a half-life of only 5,000 years to try to date rocks sandwiched between strata from the Cambrian period.