Question

According to the graph, how many atoms would remain after two half-lives?

20 atoms

80 atoms

40 atoms

50 atoms

Answer 1

Let No be initial no of atoms

N = N0 / 2 after 1 half-life

N = N0 / 4 after 2 half-lives

So after 2 half-lives 20 of the 80 atoms remain