Question

The half-life of a radioactive substance against a-decay is 1.2 × 10⁷ s. What is the decay rate for 4 × 10¹⁵ atoms of the substance-

• A. 4.6 × 10¹² atoms/s
• B. 2.3 × 10¹¹ atoms/s
• C. 4.6 × 10¹⁰ atoms/s
• D. 2.3 × 10⁸ atoms/s

Answer 1

Answer: (D)

2.3 × 10⁸ atoms/s

Answer 2

R = Nl = 4 × 10¹⁵ $\left( \frac { 0.693 } { 1.2 \times 10 ^ { 7 } } \right)$