Question

If half-Iife of radio isotope is 2 s and number of atoms is 25. The activity of a radioactive sample is measured as only 4, then after one half-life, the remaining atoms are

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

Answer: (B)

2

Answer 2

Time interval in which the mass of a radioactive substance or the number of its atoms reduces to half of life of the substance. $N = \frac{N_0}{2}$ So here, $N = \frac{4}{2} = 2$