Charcoal samples taken from holes dug at Stonehenge, England, have a carbon-14 specific activity of 9.50 dpm per gram carbon. Living wood has a specific activity of 15.3 dpm per gram of carbon.Given that the half-life of carbon-14 is 5730 yr, how long ago was the wood part of a living plant?

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The correct answer is A.The specific activity of carbon-14 in the charcoal samples is 9.50 dpm per gram carbon, and the specific activity of carbon-14 in living wood is 15.3 dpm per gram of carbon. The half-life of carbon-14 is 5730 yr.The age of the wood can be calculated using the following equation:$$t = \frac{1}{k} \ln \frac{A_0}{A}$$where:* t is the age of the wood* k is the decay constant for carbon-14 (k = 0.693/5730 yr^-1)* A_0 is the specific activity of carbon-14 in living wood (A_0 = 15.3 dpm per gram of carbon)* A is the specific activity of carbon-14 in the charcoal samples (A = 9.50 dpm per gram carbon)Plugging in the values, we get:$$t = \frac{1}{0.693/5730 yr^-1} \ln \frac{15.3 dpm per gram of carbon}{9.50 dpm per gram carbon}$$$$t = 3940 yr$$Therefore, the wood was part of a living plant 3940 years ago.

Charcoal Samples Taken from Holes Dug at Stonehenge, England, Have