Question

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

The half-life of a certain radioactive element is 1,250 years. What percent of the atoms remain 7,500 years?

a
6.25%
b
50%
c
25%
d
1.5625%

Answer 2

The correct answer is b) 2 half-lives.

In the given scenario, if 50% of the radioactive element remains after 4000 years, it means that each half-life of the element is 4000 years. Thus, in order for the remaining amount of the element to reach 50%, it would need to go through 2 half-lives, or a total of 8000 years (2 x 4000 years).

Answer 3

The correct answer is d) 1.5625%.

To calculate the percent of atoms that remain after a certain time, we can use the formula:

Percent remaining = (1/2)^(t/h) * 100

where t is the time elapsed and h is the half-life.

In this case, we have t = 7500 years and h = 1250 years.

Plugging these values into the formula, we get:

Percent remaining = (1/2)^(7500/1250) * 100
= (1/2)^6 * 100
= (1/64) * 100
= 1.5625%

Therefore, approximately 1.5625% of the atoms remain after 7,500 years.