Nuclear Decay | MCQs

Explanation

To find the time it takes to decay 75% of the initial amount, we need to find the time it takes for 25% of the initial amount to remain.

Since the half-life is 4.5 × 10^9 years, after one half-life, 50% of the initial amount remains.

After two half-lives, 25% of the initial amount remains (50% of 50%).

Therefore, the time it takes to decay 75% of the initial amount is:

2 × half-life = 2 × 4.5 × 10^9 years = 9 × 10^9 years

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.

Explanation

Lead is a chemical element.

Symbol Pb  and atomic number 82.

It is a heavy metal that is denser than most common materials.