Question

A radioactive substance decays to $\frac{1}{{16}^{th}}$ of its initial activity in 40 days. The half-life of the radioactive substance expressed in days is

• A. 2.5
• B. 5
• C. 10
• D. 20

Answer 1

The correct option is C 10

By using $N=N_0{\left(\frac{1}{2}\right)}^{t{T}_{Half}}\Rightarrow \frac{N}{N_0}=\frac{1}{16}{\left(\frac{1}{2}\right)}^{40T_{Half}}\Rightarrow T_{Half}=10days$.