Question

The activity of a radioactive sample is $1.6$ curie and its half life is $2.5days$. Then activity after $10$ days will be:

• A. $0.16$ curie
• B. $0.8$ curie
• C. $0.1$ curie
• D. $0.4$ curie

Answer 1

The correct option is C $0.1$ curie

The half life is 2.5 days.
After every 2.5 days its activity reduces to half the value.
Also, 10 days $=\frac{10}{2.5}=4$ half life periods.
The initial activity of a radioactive sample is 1.6 curie
The activity after 10 days will be
$1.6\times {\left(\frac{1}{2}\right)}^4$ $=1.6\times \frac{1}{16}=0.1$ curie.