Author Question: If the amount of radioactive element is 1/8 of the amount originally present, how many half-lives ... (Read 220 times)

Frost2351 · **on:** Jul 16, 2018

If the amount of radioactive element is 1/8 of the amount originally present, how many half-lives have gone by? Please show your work.

What will be an ideal response?

Question 2

Which is younger rock unit X or B?

What will be an ideal response?

cam1229 · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

P=Parent, D = Daughter, HL = Half-lives

P D HL
1 0 0
1/2 1/2 1
1/4 3/4 2
1/8 7/8 3
The answer is 3 half-lives have gone by.

Answer to Question 2

B is younger, otherwise it could not include pieces of X, which must have formed first.