Radioactive decay and half-life Quiz

1. A sample has 6.0 × 10¹⁰ undecayed nuclei and an activity of 3.0 × 10⁵ Bq. What is the decay constant?

• A. $2.0 \times 10^{5}$ s⁻¹
• B. $5.0 \times 10^{-6}$ s⁻¹
• C. $1.8 \times 10^{16}$ s⁻¹
• D. $5.0 \times 10^{6}$ s⁻¹

2. A source has an activity of 640 Bq and a half-life of 12 hours. What is its activity after 36 hours?

• A. 320 Bq
• B. 160 Bq
• C. 80 Bq
• D. 213 Bq

3. The decay constant of an isotope is 0.0231 min⁻¹. What is its half-life?

• A. 30 min
• B. 15 min
• C. 60 min
• D. 0.016 min

4. Which graph gives a straight line for radioactive decay?

• A. Activity against time
• B. ln (activity) against time
• C. Activity against ln (time)
• D. Half-life against time

5. Which statement about radioactive decay is correct?

• A. The decay of a particular nucleus can be predicted
• B. The decay rate depends on temperature
• C. The activity is proportional to the number of undecayed nuclei
• D. The decay constant increases as the sample decays