Question

If the number of nuclei in a radioactive sample at a given time is N, what will be the number at the end of two half-lives?

Options

• `N/2`

• `N/4`

• `(3N)/4`

• `N/8`

Answer 1

`N/4`

Explanation:

The number of nuclei in a radioactive sample at a given time is N.

After the first half-life the remaining nuclei are, `N/2`

After the second half-life the remaining nuclei are, `(N/2)/2 = N/4`