Question 223: Atoms & Nuclei

Question

The activity of a radioactive sample falls from 700 s
–1
to 500 s
–1
in 30 minutes. Its half life is close
to:

Accepted Answer

A = A
0
e
-$$\lambda $$t
$$ \Rightarrow $$ 500 = 700 e
-$$\lambda $$$$ 	imes $$30
$$ \Rightarrow $$ $$\ln {7 \over 5}$$ = $$\lambda $$$$ 	imes $$30
Also T
1/2
= $${{\ln 2} \over \lambda }$$ = $${{\ln 2} \over {\ln {7 \over 5}}} 	imes 30$$
$$ \Rightarrow $$ T
1/2
= 62 min

Answer

62 min

Answer

66 min

Answer

72 min

Answer

52 min

Atoms & Nuclei

The activity of a radioactive sample falls from 700 s –1 to 500 s –1 in 30 minutes. Its half life is close to:

Choose the correct answer: