If 50% of a radioactive element remains after 4000 years, what is the half-life? a 1 half-life b 2 half-lives c 3 half-lives d 4 half-lives

Answer 1

If 50% of a radioactive element remains after 4000 years, that indicates that one half-life has passed.

In radioactive decay, the amount of the substance remaining reduces by half for each half-life. Therefore:

• After 1 half-life, 50% remains.
• After 2 half-lives, 25% remains.
• After 3 half-lives, 12.5% remains.
• After 4 half-lives, 6.25% remains.

Since you are observing 50% remaining after 4000 years, the answer is:

a) 1 half-life.