Question

Half life of a radio active element is 8 years how much amount will be present after 32 years?

• A. $\frac{1}{4}$
• B. $\frac{1}{8}$
• C. $\frac{1}{16}$
• D. $\frac{1}{32}$

Answer 1

The correct option is C $\frac{1}{16}$

After $n$ half-lives fraction of radioactive element present is given by $\frac{1}{2^n}$

For $4$ half lives (32 years = 4 times 8 years = 4 half lives), the fraction is $\frac{1}{16}$