Answer: half life
Explanation: Radioactive decay follows first order kinetics and the time required for the decay of a radioactive material is calculated as follows:
[tex]t=\frac{2.303}{k}\hspace{1mm}log\frac{x}{a}[/tex]
t= time required
k= disintegration constant
x= amount of substance left after time t
a= initial amount of substance
when one half of the sample is decayed, one half of the sample remains and t can be represented as [tex]t_{1/2}[/tex]
at [tex]t= t_{1/2}[/tex], [tex]x=\frac{a}{2}[/tex]
[tex]t_{1/2}=\frac{2.303}{k}\hspace{1mm}log\frac{a/2}{a}[/tex]
[tex]t_{1/2}=\frac{0.693}{k}[/tex]
