Question

The half-life of an isotope of tritium is 4500 days. How many days will it take an amount of tritium to fall to a quarter of its initial mass?

year 9 question

Answer 1

9000 days.

Explanation:

Decay can be described by the following equation:

`M_0="initial mass"`

`n`=number of half lives

`M=M_0 times (1/2)^n`

`(1/4)=1 times (1/2)^n`

`(1/4)=(1^2/2^2)`

So `n=2`, which means 2 half-lives must have passed.

1 half-life is 4500 days, so it must take `2 times 4500=9000` days for the sample of tritium to decay to a quarter of its initial mass.