Ancient paintings were found on cave walls in South America. The Carbon-14 in the paintings was measured and was found to be 19% of the original weight. How old were the paintings?

Respuesta :

Answer:

Painting is 13725 years old.

Step-by-step explanation:

C-14 dating is the process through which age of fossils or dead tissues are determined.

One important thing about the C-14 dating is half life life period of C-14 that is 5730 years.

Now we know for C-14 decay we use the formula

[tex]A_{t}=A_{0}e^{-kt}[/tex]

where [tex]A_{t}[/tex] = present quantity of C-14

[tex]A_{0}[/tex] = Initial quantity of C-14

k = Decay constant

t = Duration or time

We will calculate the decay constant first to use this formula for age determination further.

For Half life of C-14

A_{t}=A_{0}e^{-kt}

[tex]\frac{1}{2}=1.e^{-k(5730)}[/tex]

Taking ln on both the sides

[tex]ln(\frac{1}{2})=ln(1.e^{-k(5730)})[/tex]

[tex]-ln2=-5730k(lne)[/tex]

k = [tex]\frac{ln2}{5730}=(1.21)(10)^{-4}[/tex]

Now we have been given in the question that C-14 found to be 19% and we have to determine the age of the painting.

[tex]A_{t}=A_{0}e^{-kt}[/tex]

[tex]0.19=1\times (e^{-(1.21\times 10^{-4})t})[/tex]

We will take ln on both the sides

[tex]ln(0.19)=ln[1\times (e^{-(1.21\times 10^{-4})t})][/tex]

[tex]-1.6607=-(1.21\times 10^{-4})t\times lne[/tex]

[tex]t=\frac{1.6607}{1.21\times 10^{-4}}[/tex]

t = 1.3725×[tex]10^{4}[/tex]

t = 13725 years

Therefore, painting is 13725 years old.

 

Answer:

13713.717 years

Step-by-step explanation:

The exponential decay model for Carbon-14 is modeled by the following formula:

[tex] A=A_{0}\;e^{-0.0001211\;t} [/tex]

where:

[tex]A_0[/tex] is the initial amount of Carbon-14

A is the final amount of Carbon-14, [tex]A = 0.19 \times A_0[/tex]

t is the elapsed time in years since the painting was made

Replacing in the formula:

[tex] 0.19 \times A_0=A_{0}\;e^{-0.0001211\;t} [/tex]

[tex] 0.19=e^{-0.0001211\;t} [/tex]

[tex] ln(0.19)=-0.0001211\;t [/tex]

[tex] \frac{ln(0.19)}{-0.0001211}=t [/tex]

[tex] 13713.717 years=t [/tex]