d) Carbon dating

h) radioactive dating, e.g. carbon-dating

the production of carbon-14

• the sun emits protons

• collide with atoms in the atmosphere

• atoms emit neutrons

• neutrons collide with nitrogen-14

• form carbon-14

the existence of carbon-14 and carbon-12 inside an organism

• in a living organism, the ratio of carbon-14 to carbon-12 is 1.3 × 10^-12

• after the organism dies

  • the amount of carbon-12 remains constant

  • carbon-14 continues to decay

  • the ratio decreases

carbon-dating

• activity is directly proportional to the number of undecayed nuclei

• determine the activity or the number of undecayed nuclei of the carbon-14

• N = N0e^-λt, A = A0e^-λt

limitations of carbon-dating

• assumes that the ratio of carbon-14 to carbon-12 has remained constant

• cannot be used to date rocks

  • the existence of rocks is much longer than the half-life of carbon-14