Question

What are the units of a half-life?

Answer 1

The units of half-life are time.

Explanation:

The units of half-life are time. The half-life is the length of time that it takes for half of an initial sample to undergo a change. Usually this is the radio-active decay of a specific atomic weight of an element. For example, the half-life of Uranium-238 is 4.46 billion years.

The formula for half-life which gives the number of remaining atoms after a time, `t`, and starting with `N(0)` atoms in the sample:

`N(t) = N(0) (1/2)^(t/t_(1//2))`

where `t_(1//2)` is the half-life in units of time. This is clear from the formula, since the power must be unitless, so the units of half-life must cancel with the units of the time, `t`.