Next, we'll take the natural logarithm of each of these quantities.
For example, the biological half-life of water in a human being is about 9 to 10 days, citation needed though this can be altered by behavior and various other conditions.
A half-life usually describes the decay of discrete entities, such as radioactive atoms.
Thus, the mixture taken as a whole will not decay by halves.
In other words, the probability of a radioactive atom decaying within its half-life.
A quantity of carbon-14 will decay to half of its original amount ( on average ) after 5,730 years, regardless of how big or small the original quantity was.
5 While a radioactive isotope decays almost perfectly according to so-called "first order kinetics" where the rate constant is a fixed number, the elimination of a substance from a living organism usually follows more complex chemical kinetics.In this case, the actual half-life T 12 can be related to the half-lives t 1 and t 2 that the quantity would have if each of the decay processes acted in isolation: 1 T 1 / 2 1 t 1 1 t 2 displaystyle.Demos Medical Publishing, LLC.The Drax Files: World Makers video series and hear from some of the people creating and doing amazing things in Second Life.N ( t ) is the quantity that still remains and has user guide to ipad not yet decayed after a time t, t 12 is the half-life of the decaying quantity, is a positive number called the mean lifetime of the decaying quantity, is a positive number called.2 3 4 Formulas for half-life in exponential decay edit Main article: Exponential decay An exponential decay can be described by any of the following three equivalent formulas: N ( t ) N 0 ( 1 2 ) t t 1 / 2 N (.Note that after one half-life there are not exactly one-half of the atoms remaining, only approximately, because of the random variation in the process.See List of nuclides.