Question

For a radioactive material, half-life is $10$ minutes. If initially there are $600$ number of nuclei, the time taken (in minutes) for the disintegration of $450$ nuclei is?

• A. $30$
• B. $20$
• C. $15$
• D. $10$

Answer 1

The correct option is B $20$

Half life $=10min=\frac{ln2}{\lambda }$

Nuclei disintegrate = 450

Nuclei left = 600-450 =150

$N=N_o{e}^{-\lambda }t$

$150=600e^{\frac{-ln2}{10}t}$

so, t = 20 minutes