Question

The half-life of cobalt 60 is 5.26 years. The percentage activity remaining after 4 years is ______%.

Options

• 45

• 50

• 53

• 60

Answer 1

The half-life of cobalt 60 is 5.26 years. The percentage activity remaining after 4 years is 53%.

Explanation:

λ = `2.303/"t" log  "N"_0/"N"`

`0.693/("t"_(1/2)) = 2.303/"t" log  "N"_0/"N"`

`0.693/60 = 2.303/5.26 log  "N"_0/"N"`

∴ % activity remaining = 53%