Question

The half life period of radium is 1600 years. The fraction of a sample of radium that would remain after 6400 years is.

• A. $\frac{1}{4}$
• B. $\frac{1}{2}$
• C. $\frac{1}{8}$
• D. $\frac{1}{16}$

Answer 1

Answer: (D)

$\frac{1}{16}$

Answer 2

Fraction $= \frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{\frac{6400}{1600}} = \left( \frac{1}{2} \right)^{4} = \frac{1}{16}$.