Question

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

• A. 0.693
• B. 0.63
• C. 0.5
• D. 0.37

Answer 1

Answer: (B)

0.63

Answer 2

N = $N_0e^{-\lambda t} = N_1 e^{- \lambda / \lambda} = \frac{N_0}{e} = 0.37 N_0$
$\therefore$ decayed = 63% ($\because$ e = 2.718)