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Decay Constant of Copper 66

  1. Nov 17, 2011 #1
    2. Relevant equations
    I was given all this information... I cannot figure it out whatsoever. I would post my attempts but there were too many. Any ideas would be helpful. I know the answer is 5.09 as the half life
    Decay Constant of Copper 66



    Sources do not emit radiation at a constant rate but fade away with time.

    In this experiment, you monitor the count rate of a sample of copper 66 which has just been prepared.

    The detector counts for one minute at each interval.


    time(minutes) counts
    0 ------------932
    1 -------------813
    2 -------------710
    3 -------------619
    4------------ 540
    5------------ 453
    6 ------------435
    -
    time(minutes) counts
    7 ---------359
    8 -----------318
    9 ---------266
    10 ----------239
    11 ----------205
    12 ------------182
    13 ------------161

    time(minutes) counts
    14 ------------138
    15 ------------121
    16 --------------108
    17 ------------92
    18-------------- 80
    19 ------------70
    20 ------------61




    The data in the table should satisfy the relation:

    N=N0e-(lambda)t
    where, N0 = the number of counts at time 0

    N = the number of counts after an elapsed time T

    lambda = the decay constant for the specific isotope

    t = the elapsed time


    Plot the count rate vs the time on semilog paper using the data found in the table. Calculate the slope.
    Hint#1: Make sure you calculate the slope in the right units and that the sign of the answer make sense.

    Hint#2: From the formula above the value of the slope will be "-lambda"

    Be sure to enter the answer in the summary table in your lab outline.

    The half-life, T, is defined as the time for the count rate to drop by a factor of 2.

    (1/2)N0 = N0e^-(lambda)T
    T = 0.693/lambda

    1. The problem statement, all variables and given/known data

    i cannot find the half life/slope

    2. Relevant equations
    equations above


    3. The attempt at a solution
    my attempts were not posted because it would make this uber long
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Nov 17, 2011 #2

    Delphi51

    User Avatar
    Homework Helper

    Welcome to PF, Sarah.
    So, you have a graph but can't find its slope?
    Put "how to find the slope of a graph" into Google.
    If you scan your graph and post it here, we can help you with it.
    It will be easiest if you do the graph with a spreadsheet. Just capture the window with alt+printScreen, paste into a paint program, save and upload. Uploading to a service like Photobucket works really well. Then you can paste an IMG link here.

    If that is too much work, tell us the coordinates of two points on your line of best fit.
     
  4. Nov 18, 2011 #3
    Yes, I know how to find the slope but can I not find it with the equations I have and the information I have, or else there would be no point to this assignment because I am in University so...I doubt they would just ask me to find the slope...
     
  5. Nov 19, 2011 #4

    Delphi51

    User Avatar
    Homework Helper

    Yes, they HAVE just asked you to find the slope!
    Of course you have to draw the graph on log paper to get a straight line.
     
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