Explain how half life is used in radioactive dating
In order to use these methods, we have to start out with a system in which no daughter element is present, or else know how much daugher element was present initially so that it can be subtracted out.
We also need to know that no parent or daughter has entered or left the system in the meantime.
This gives us the impression that all but a small percentage of the dates computed by radiometric methods agree with the assumed ages of the rocks in which they are found, and that all of these various methods almost always give ages that agree with each other to within a few percentage points.Assuming we start out with pure parent, as time passes, more and more daughter will be produced. A ratio of infinity (that is, all daughter and no parent) means an age of essentially infinity.By measuring the ratio of daughter to parent, we can measure how old the sample is. Each radioactive element has a half-life, which tells how long it takes for half of the element to decay.Potassium 40 (K40) decays to argon 40, which is an inert gas, and to calcium.Potassium is present in most geological materials, making potassium-argon dating highly useful if it really works.
Potassium is about 1/40 of the earth's crust, and about 1/10,000 of the potassium is potassium 40.