## Appendix: 3. Half-life

Half-life, , as introduced previously, is the time it takes for the mass of a substance to decay by half.

At this point, we know that . Using this relation, we can express half-life in terms of or vice versa.

Firstly, we consider to be . Then, . Now our relation, simplifies.

Simplify the relation to express half-life, , in terms of .

Thus, by knowing the half-life of a substance, we can find , and model the decay of the substance using the exponential decay equation .

Given that a substance has a half-life of 10 units of time, find .

Given that a substance has a half-life of 5 units of time, find .

Using the values of that you calculated, which of the two curves (if you graphed them using the values of ) produced would approach 0 more rapidly?

Was it necessary to calculate the values of to answer the above question?