Question

A certain radioactive substance has a half-life of 5 years. Thus for a nucleus in a sample of the element, the probability of decay in ten years is-

• A. 50 %
• B. 75 %
• C. 100 %
• D. 60 %

Answer 1

Answer: (B)

75 %

Answer 2

In two half-lives, the material that remains undecayed is $\frac { 1 } { 4 }$th, i.e. 25%. Hence percentage of decayed material = 75%