In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life ?

Options

A. `69. 3 %`
B. 0.63
C. 0.5
D. 0.37

Answer

B

Explanation

(b) Number of atoms remains undecayed `N = N_0 e^(- lamda t)`
Number of atoms decayed `= N_0(1 - e^(- lamda t))`
=`N_0(1 - e^(-lamda xx (1)/(lamda))) = N_0 (1 - (10)/( e))`
=`0.63 N_0 = 63 % of N_0`.