d) Carbon dating

• the production of carbon-14

• the sun emits protons

• protons collide with atoms in the atmosphere

• atoms emit neutrons

• neutrons collide with nitrogen-14

• this forms carbon-14

• the life process of carbon-14 and carbon-12 in the body of a living 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 carbon12 remains constant

  • carbon14 begins to decay

  • the ratio decreases

• the carbon-dating process

• activity is directly proportional to the number of undecayed nuclei

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

• N=N0e^-λt, A=A0e^-λt

• the 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