physics

posted by .

Radioactive nuclei are produced in an irradiated sample at the rate of 10 s-1. If the number in the sample builds up to a maximum of 1000, calculate the mean life and the half-life of the radioactive nuclei

Using dN / dt = P - λ N

dN / dt = 1000n /10/ 1 = 100
P - λ N = 10 – λ 1000N

Half life is -

(In2) / λ = (In2) / 1000) = 6.93x10^-4 seconds

Not sure of mean life any advice appreciated ...

  • physics -

    if none were added
    dN/dt = k N

    number produced per second = 10
    number lost per second = k n

    so
    dN/dt = 10 - k N
    N is maximum when dN/dt = 0
    0 = 10 - k (1000)
    k = .01

    so we know that for this fission reaction (without the inflow)
    dN/dt = -.01 N
    dN/N = -.01 dt
    ln N = -.01 t + C
    N = Ni e^-(.01 t)

    when is N/Ni = .5?
    ln .5 = -.01 t
    t = 69.3 seconds half life

    mean life = 1.443 * half life (see http://www.britannica.com/EBchecked/topic/371549/mean-life )

  • physics -

    THANK YOU .....

  • physics -

    You are welcome :)

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. physics-Radioactivity

    1) The number of radioactive nuclei in a particular sample decreases over a period of 15 days to one-seventeenth the original number. What is the half-life (in days) of these nuclei?
  2. physics

    Suppose 32000 radioactive nuclei are in a sample. About how many remain after two days if the half-life is 22 hrs?
  3. Pre-Cal

    The radioactive isotope of Carcon (^14C)has a half life of 5730. What is the decay constant of ^14C?
  4. Chemistry

    How many half lives will it take for a sample of a radioactive isotope containing 20000 radioactive nuclei to decay to 2000 radioactive nuclei
  5. phys

    Although most natural potassium nuclei are stable 39K (93.3%) or 41K (6.7%) nuclei, about 0.0117% are radioactive 40K nuclei, which have a half-life of 1.26 billion years. What fraction of all the potassium nuclei in your body will …
  6. physics

    116In nuclei are produced at the rate of 10 s-1. Calculate the maximum number of 116In nuclei (number in equilibrium) in the sample if the half-life of 116In is 54 m. So far I have come up with ... The half life = 54m x 60 s-1 = 3.24 …
  7. science

    116In nuclei are produced at the rate of 10 s-1. Calculate the maximum number of 116In nuclei (number in equilibrium) in the sample if the half-life of 116In is 54 m. So far I have come up with ... The half life = 54m x 60 s-1 = 3.24 …
  8. Physics ...

    116In nuclei are produced at the rate of 10 s-1. Calculate the maximum number of 116In nuclei (number in equilibrium) in the sample if the half-life of 116In is 54 m. So far I have come up with ... The half life = 54m x 60 s-1 = 3.24 …
  9. SCIENCE

    We did a radioactive decay and half life lab with m&ms and I do not understand these conclusion questions: 1. how many half lives would it take for 500 nuclei to decay to 6.25% of the original number of nuclei?
  10. physics

    The number of radioactive nuclei present at the start of an experiment is 3.27 x 1015. The number present twenty days later is 7.66 x 1014. What is the half-life (in days) of the nuclei?

More Similar Questions