Question

The ratio activity of an element becomes 1/64^th of its original value in 60 sec. Then the half life period is.

• A. 5 sec
• B. 10 sec
• C. 20 sec
• D. 30 sec

Answer 1

Answer: (B)

10 sec

Answer 2

$A = A_{0}\left( \frac{1}{2} \right)^{\frac{t}{T_{1/2}}} \Rightarrow \frac{1}{64} = \left( \frac{1}{2} \right)^{\frac{60}{T_{1/2}}}$

$\Rightarrow \left( \frac{1}{2} \right)^{6} = \left( \frac{1}{2} \right)^{\frac{60}{T_{1/2}}} \Rightarrow T_{1/2} = 10\sec$.