Explanation

Question: A powder contains 100mg of a radioactive material that emits α-particles. The half-cycle of the isotope is five days. The mass of isotope that remains after ten days will be?

Answer: The half-life of the isotope is 5 days, which means that every 5 days, half of the remaining material decays. After 10 days, there will be two half-lives:

1. First half-life (5 days): 100mg → 50mg (half of the material decays)
2. Second half-life (next 5 days): 50mg → 25mg (half of theq remaining material decays)

So, after 10 days, 25mg of the original 100mg will remain.