adiocarbon dating of blackened grains from the site of ancient Jericho provides a date of 1315 BC ± 13 years for the fall of the city. What is the relative amount of 14C in the old grain vs the new grain in 2007 AD? (A0 = original radioactivity; At = radioactivity in 2007 AD).

Respuesta :

Answer:

[tex]\left(\frac{m(t)}{m_{o}} \right)_{min} \approx 0.659[/tex] and [tex]\left(\frac{m(t)}{m_{o}} \right)_{max} \approx 0.661[/tex]

Step-by-step explanation:

The equation of the isotope decay is:

[tex]\frac{m(t)}{m_{o}} = e^{-\frac{t}{\tau} }[/tex]

14-Carbon has a half-life of 5568 years, the time constant of the isotope is:

[tex]\tau = \frac{5568\,years}{\ln 2}[/tex]

[tex]\tau \approx 8032.926\,years[/tex]

The decay time is:

[tex]t = 1315\,years + 2007\,years \pm 13\,years[/tex] (There is no a year 0 in chronology).

[tex]t = 3335 \pm 13\,years[/tex]

Lastly, the relative amount is estimated by direct substitution:

[tex]\frac{m(t)}{m_{o}} = e^{-\frac{3335\,years}{8032.926\,years} }\cdot e^{\mp\frac{13\,years}{8032.926\,years} }[/tex]

[tex]\left(\frac{m(t)}{m_{o}} \right)_{min} = e^{-\frac{3335\,years}{8032.926\,years} }\cdot e^{-\frac{13\,years}{8032.926\,years} }[/tex]

[tex]\left(\frac{m(t)}{m_{o}} \right)_{min} \approx 0.659[/tex]

[tex]\left(\frac{m(t)}{m_{o}} \right)_{max} = e^{-\frac{3335\,years}{8032.926\,years} }\cdot e^{\frac{13\,years}{8032.926\,years} }[/tex]

[tex]\left(\frac{m(t)}{m_{o}} \right)_{max} \approx 0.661[/tex]