Question

A certain radio active 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

The correct option is B $75\%$

In 10 years the number of undecayed particles will be N0/4N0/4. That number of decayed particles will be 3 N0/4N0/4.

Hence probability of decay will be 75%

Option B is right