Question

A radioactive substance has an average life of 5 hours. In a time of 5 hours.

• A. Half of the active nuclei decay
• B. Less than half of the active nuclei decay
• C. More than half of the active nuclei decay
• D. All active nuclei decay

Answer 1

Answer: (C)

More than half of the active nuclei decay

Answer 2

If $\lambda$is the decay constant of a radioactive substance than average life = $\frac{1}{\lambda}$

Also half life $= \frac{0.693}{\lambda} = 0.693 \times (Average\mspace{6mu} life)$

in single average life, more than 63% of radioactive nuclei decay.