Question

Half-life of a substance is 20 minutes. What is the time between $33\%$ decay and $67\%$ decay

• A. 40 min
• B. 20 min
• C. 30min
• D. 25 min

Answer 1

The correct option is B

20 min

$t_{\frac{1}{2}}=20min(100-33)=\frac{N_0}{2^{n_1}}(100-67)=\frac{N_0}{2^{n_2}}\frac{67}{33}=2^{n_2-n_1}2=2^{n_2-n_1}{n}_2-n_1=1t_2-t_1=t_{\frac{1}{2}}$