Radioactivity

Lab 7 Notes

The corrected graph now appears in the lab web page but not in the video. Ignore the video as far as half life claim at 4000 years as like I stated in ATP, the narrator was using an incorrect graph.

Radioactive decay is a very useful tool in physics and has many real world applications. So what you are going to do this week is look at a plot if a radioactive decay and determines time lines and eventually the isotope in question.

1) Determine the half-life of this isotope using the equation 

where  is the half-life.

2) Determine how many particles are present at 4000, 6000, 8000 and 10000 years using the graph and the equation.

3) What are some applications of an isotope like this?

4) Once you have the half-life, what do you think this isotope is?

 

Lab 7:

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Radioactivity  Lab week 7:  Besides the formal write up as usual, you may use the graph from the lab to draw projections to y and x axis to aid you answering the questions under the graph. You should use the N = N0 e-t/T equation where N is the amount of particles or mass you have, N0 the amount you started with, t is the decay constant and T the half-life or the time for the particles or mass to decrease by 1/2. HINT: t can be chosen from graph to be anything just note the t you pick to go with how many particles. WHY? Because N will be some fraction of N0.  So? Algebra folks. What happens when you have the same variable on both sides of the equation and how you simplify that equation?  You will then calculate the half-life and look up in your book what element it is. Answer ALL the questions please.  UPDATE PLEASE READ NOW!   There was a serious error in the graph originally supplied in the course by course creators. I have managed to get IT to fix the graph BUT they have yet to fix the video.  My apologies.   I spent a lot of time thinking about this graph and I have come to the conclusion that it is plain wrong because of the x axis. Note now that the half life of this element sticks out as it should. Use the equation I give you in the excel file to show it predicts the values for the points I gave you. You should see on the graph  those years by just following the trace.  I want you to use 1000 particles for the starting value where I call the fraction 1. That means when you look at 1/2 that would be 500, 1/4 250.  You are NOT going to predict the particle count for 4000, 6000, 8000, 10000 years you did with the old graph. Just verify the formula will give you the points I show. I give you the lambda.   We are coming to the end of the course. I apologize for this error as I respect your time. I did not cause the error but take responsibility for it. It has been a long time in dispute because if you claim Tau is the half life as the author does in the video experiment, then t is just any time. The formula would then give the right half life BUT that graph is just plain wrong.

Let me know if you still have questions. PLEASE NOTE!  The element if not going to be Mo!!!!!!  If you get that conclusion you did not read what I wrote above to do the lab right.