Biology Doubt! Carbon 14 problem?
The half-life for Carbon-14 is 5730 years. A fossil has been dated to be 17 190 years old and the amount of Carbon-14 was determined in 0.0375mg. The initial amount of Carbon-14 in the sample was:
a)0.90mg
b)0.030mg
c)0.30mg
d)0,0046875mg
Comments
c)0.30mg
3 half lifes have elapsed: elapsed time / half life = elapsed half lives
17190 / 5730 = 3
Each half life cuts in half the amount of C-14 remaining. 3 half lives have passed, so there is now (1/2)^3 = 1/8 as much C-14 as there initially was. So to get back to the initial amount, we just multiply the current amount by 8.
initial = 8 * current
Initial = 8 * 0.0375mg
initial = 0.30mg
The answer is c) .30mg
As the sample is 17190 old , this means it has passed through 3 half lives as 17190/5730=3
Therefore now you know that the sample has halved three times so just multiply it by 2 three times
.0375*2*2*2=.3mg
If you like my answer pls check out a video i made at-
http://www.youtube.com/watch?v=7bZ1WsI_6FM