A rock sample containing radioactivity was found to have only 1/8 of the amount of the original substance that it did when it was formed. How many half-lives have elapsed since the rock was formed?
A. 2
B. 1
C. 0
D. 3
E. 8
2007-01-17 04:34:34 · 5 answers · asked by Rattiesrule 2 in Science & Mathematics ➔ Biology
D, of course!
Edited to explain.
The rock started out at full radioactivity, or 8/8.
After the first half-life, it was 4/8.
The second half-life would be 2/8.
And the third and current half-life would have brought it to1/8.
2007-01-17 04:38:21 · answer #1 · answered by we2inmaine 2 · 2⤊ 0⤋
D, since 1/8 = 2^-3
2007-01-17 04:40:04 · answer #2 · answered by poorcocoboiboi 6 · 1⤊ 0⤋
It's called half life for a reason: after 1 half-life you have one- half of the material left, after 2 half lives (1/2 * 1/2 = 1/4), after 3 half lives (1/4*1/2 =1/8) and so on
2007-01-17 04:41:44 · answer #3 · answered by lynn y 3 · 0⤊ 0⤋
what a simple math question: the answer is D
2007-01-17 04:43:02 · answer #4 · answered by c4n7_b3_ur_5up3rm4n 2 · 0⤊ 0⤋
D
Something a bit more challenging or interesting please.
2007-01-17 04:45:15 · answer #5 · answered by gebobs 6 · 0⤊ 0⤋