Question 162: Atoms & Nuclei

Question

The activity of a radioactive material is $6.4 	imes 10^{-4}$ curie. Its half life is 5 days. The activity will become $5 	imes 10^{-6}$ curie after :

Accepted Answer

$\because$ $A = {{{A_0}} \over {{2^{{t \over {{T_{1/2}}}}}}}}$
$ \Rightarrow {2^{t/5}} = {{6.4 	imes {{10}^{ - 4}}} \over {5 	imes {{10}^{ - 6}}}} = 128 = {2^7}$
$ \Rightarrow {t \over 5} = 7$
$ \Rightarrow t = 35$ days

Answer

7 days

Answer

15 days

Answer

25 days

Answer

35 days

Atoms & Nuclei

The activity of a radioactive material is 6.4 \times 10^{-4} curie. Its half life is 5 days. The activity will become 5 \times 10^{-6} curie after :

Choose the correct answer: