Question

A radioactive element X with half life 2 h decays giving a stable element Y. after a time t, ratio of X and Y atoms is 1 : 16 time t is.

• A. 6 h
• B. 4 h
• C. 8h
• D. 16h

Answer 1

Answer: (C)

8h

Answer 2

: $\frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{n} = \frac{1}{16}$

$\therefore n = 4$

$t = nT_{1/2} = 4 \times 2 = 8h$