Question

Half life of a radioactive element is 10 days. The time during which quantity remains 1/10 of initial mass will be.

• A. 100 days
• B. 50 days
• C. 33 days
• D. 16 days

Answer 1

Answer: (C)

33 days

Answer 2

After three half lives (i.e., 30 days) it remains $\left( \frac{1}{2} \right)^{3} = \frac{1}{8},$ so it will remain $\frac{1}{10}th$, approximately in 33 days.