Question

A radioactive sample has half life of 5 years. Probability of decay in 10 years will be:

• A. $100\%$
• B. $75\%$
• C. $50\%$
• D. $25\%$

Answer 1

Answer: (B)

Number of half lives $n=\frac{10}{5}=Z,$
Now $\frac{N}{N_0}={\left(\frac{1}{2}\right)}^2=\frac{1}{4}$
Fraction decayed $=1-\frac{N}{N_o}=1-\frac{1}{4}=\frac{3}{4}$
In percentage $=\frac{3}{4}\times 100=75\%$