Question

Half-life of a nuclide is $20$ days. After $40$ days the amount of substance left will be:

• A. $1/2$
• B. $1/4$
• C. $1/8$
• D. $1/16$

Answer 1

The correct option is B $1/4$

After two half lives, amount will $(\frac{1}{2}{)}^2$ of the initial amount.