Question

Suppose that the half-life of an element is 1000 years. How many half-lives will it take before one-eighth of the original sample remains?

8
125
12.5
3

Answer 1

the answer is 3

Step-by-step explanation:

Answer 2

3

Step-by-step explanation:

The half-life of a radioactive isotope is the time it takes for the mass of the sample to halve.

This can be rewritten as follows:

`m(t) = m_0 ((1)/(2))^n`

where

m(t) is the mass of the sample at time t

m0 is the original mass of the sample

n is the number of half-lives that passed

We see that if we take n=3, the amount of original sample left is

`m(t) = m_0 ((1)/(2))^3 = m_0 ((1)/(8))`

So 3 (3 half-lives) is the correct answer.