Question

The amount of radioactive carbon-14 in a sample is measured using a Geiger counter, which records each disintegration of an atom. Living tissue disintegrates at a rate of about 13.5 atoms per minute per gram of carbon. In 1977 a charcoal fragment found at Stonehenge, England, recorded 8.2 disintegrations per minute per gram of carbon. Assuming that the half-life of carbon14 is 5730 years and that the charcoal was formed during the building of the site, estimate the date when Stonehenge was built

Answer 1

4121 years

Step-by-step explanation:

From;

0.693/t1/2 = 2.303/t log No/N

t1/2= half life of the carbon-14

No= count rate of the living tissue

N= count rate of the sample

t = age of the sample

0.693/5730 =2.303/t log (13.5/8.2)

1.21 * 10^-4 = 2.303/t * 0.2165

1.21 * 10^-4 = 0.4986/t

t = 0.4986/1.21 * 10^-4

t = 4121 years