Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Nuclear physics

  1. Jul 24, 2007 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    This is the question which I'm working on:
    When an animal dies the radioctive carbon content of its body has an activity of 12 counts per gram per minute. Some animal remains are found to have an activity of 3 counts per gram per minute. If the half life of radioactive carbon id 5000 years,how old are the animal remains.

    My solution:
    Decay rate reduced from 12counts/gram/min to 3counts/gram/min. Therefore it must have passed 2 half-lives. So two half-lives must be 5000 x 2 = 10 000.
    Is my method right?
  2. jcsd
  3. Jul 24, 2007 #2
    Yes, your method is right.

    It can also be written as R=[tex]R_{0}[/tex] [tex]e^{-\lambda t}[/tex]

    where the total decay rate R of a sample of one or more radionucclides is called the activity of that sample.
  4. Jul 24, 2007 #3


    User Avatar
    Science Advisor
    Homework Helper

    Yes you are correct.
    The formula is a little more complicated if the animal didn't have the consideration to die a whole number of half-lifes ago!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook