1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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 decay

  1. Oct 8, 2011 #1
    Problem is:

    have a mother and daughter sample, [tex]A[/tex] and [tex]B[/tex] respectively. both are radioactive. The number of daughter nuclei at time t is given by (*):


    where N_0 is number of mother nuclei at t=0 and n(t) is number of daughter nuclei at time t.

    A has [tex]\tau_{\frac{1}{2}}=23minutes[/tex] and B has [tex]\tau_{\frac{1}{2}}=23days[/tex].

    A is beta only emitter. B emits gamma and Beta. If A has been made and purified and 11.5minutes after this, the sample emits 1000 gammas/second and some time later the sample again emits 1000 gammas/second - how much time has elapsed?

    My Thoughts:
    I don't know how to handle this problem for the following reason: To find the rate of gammas being emitter, simply differentiate the equation I showed above (*) to get:


    (note can find the lambda_A and lambda_B as we know the half-llife and can also solve (*) for N_0).

    The time dependance of the above equation is a negative exponential... so to solve for t, do some rearranging, and take the natural log... but this will be a linear equation... ie. there will only be one value of t for any dn/dt so it is not clear to me how at 11.5mins can have 1000 gammas/second and then again some time later can also have 1000 gammas/second.

    What to do?
    Last edited: Oct 8, 2011
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted