High energy cosmic rays from space hit the nitrogen in the atmosphere and convert it from nitrogen (N14) into carbon (C14). This produces a steady concentration of C14 in the atmosphere once the decay rate of the C14 back into N14 matches the conversion rate from the cosmic ray flux (which is assumed to be constant for reasons you can ask me about if you want). a) What kind of radiation (what kind of particle) does the C14 emit when it decays? Tell me how you know? b) The concentration of C14 in plants (and animals) comes into equilibrium with the atmosphere because living things use the ambient carbon to make their cellular structures. However, once a plant dies, it no longer consumes C14. The C14 starts to decay away— allowing us to calculate when the plant died because the C14/C12 ratio doesn’t match the atmosphere. If the half life of C14 is 5000 years, what is the age of a piece of charcoal from a site from the Clovis peoples of North America if the concentration of C14 is 15% of the equilibrium value?
High energy cosmic rays from space hit the nitrogen in the atmosphere
and convert it from nitrogen (N14) into carbon (C14). This produces a steady
concentration of C14 in the atmosphere once the decay rate of the C14 back into
N14 matches the conversion rate from the cosmic ray flux (which is assumed
to be constant for reasons you can ask me about if you want).
a) What kind of
me how you know?
b) The concentration of C14 in plants (and animals) comes into equilibrium with the atmosphere because living things use the ambient carbon to make their cellular structures.
However, once a plant dies, it no longer consumes C14. The C14 starts to decay away—
allowing us to calculate when the plant died because the C14/C12 ratio doesn’t match the
atmosphere. If the half life of C14 is 5000 years, what is the age of a piece of charcoal from
a site from the Clovis peoples of North America if the concentration of C14 is 15% of the
equilibrium value?
c) A similar process is used to measure the ages of rocks. Some minerals will incorporate
Uranium in their structures, but they will not incorporate Lead. Uranium is radioactive
and eventually decays into Lead. Thus, we can look at the minerals and measure the Lead
content to determine how long ago the Uranium was incorporated into the original material.
Isn’t that awesome? (True or False)
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