

Topics: Radioactive decay, radioactivity,
exponential rate. Prerequisite skills: Knowledge of the exponential function. Approximate completion time: Under an hour. 

Provide sufficient detail to verify that the assignment was completed in a meaningful manner. 

Applet by FuKwun Hwang 

The above applet originally displays 1950 black circles, each
representing a radioactive isotope. The half life is entered in the text box.
These black isotopes will decay into green isotopes, which are not shown in
the applet window. 1. Check the box on the far right of the applet. This will create a twostep decay process (black to white). Set the value for tau1 = 10 (the halflife of the black isotopes) and run the applet. The black line plots the number of black isotopes remaining (the red line has no meaning in this part of the assignment). . (a) What percentage of the black isotopes should have decayed after 10 seconds? (b) The first horizontal tic represents 10 seconds in this part of the assignment. Using the mouse, place the cursor on the black line directly above the first horizontal tic mark. According to the display, how many black isotopes remain? How does this value compare to the value predicted in Question 1(a). 2. Remove the check in the small box at the upperright of the applet. Also, set tau3 and tau4 equal to 0. This will turn the radioactive series into a black, to red, to blue sequence.
3. The relationship between the number of isotopes remaining after a time t is given by
where N_{0} is the original number of isotopes and T is a constant that determines the rate of decay.


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