Question

A sample contains 16 gm of a radioactive material, the half life of which is two days. After 32 days, the amount of radioactive material left in the sample is.

• A. Less than 1 mg
• B. $\frac{1}{4}gm$
• C. $\frac{1}{2}gm$
• D. 1 gm

Answer 1

Answer: (A)

Less than 1 mg

Answer 2

Remaining amount

$= 16 \times \left( \frac{1}{2} \right)^{32/2} = 16 \times \left( \frac{1}{2} \right)^{16} = \left( \frac{1}{2} \right)^{12} < 1\mspace{6mu} mg$.