Using bar charts, this applet shows the relative abundances of the significant nuclei in one of four different radioactive decay series (Th232, Pu241, U238, U235) as functions of time. The user selects one radioactive decay series.
Type of Material:
Simulation, Java applet.
Lecture Demo or Homework
Identify Major Learning Goals:
An understanding of basic radioactive decay processes, lifetimes, half lives, and plotting on a LOG scale.
Target Student Population:
Secondary and Lower Level Undergraduate.
Prerequisite Knowledge or Skills:
Sufficient algebra to work with half lives. Radioactive decay equations, half-life, logarithmic plots.
Evaluation and Observation
Displays a bar graph showing relative abundance of each of the elements in the decay sequence. The decay time step can be selected. The user can stop the process and observe a table at the right that contains abundance data for that time. Thus decay data can be collected by students.
The bar graphs provide a clear indication of the relative abundances of the various nuclei at any given time. Several sequences are selectable, as well as the decay time step.
The plot displays on a LOG scale, but there is no numerical display on the axis indicating that it is a LOG scale.
The exponent in the "RealTime" text box is cut off (and unscrollable), so that it is of little use.
Potential Effectiveness as a Teaching Tool
Students can actually collect data. Then can be instructed to make a plot. To make use of this applet students will need to get out pen and paper and make a graph, or make their own on a computer. The applet does not do the work for them.
The clearly changing and different heights of the bars may induce curiosity in students to know why. The ability to stop the applet at various times allows for quantitative calculations (if one could see the elapsed time).
The effectiveness of this applet is very highly dependent upon how it is used by the instructor. Students will learn little from watching the bars grow or shrink. The instructor will need to take the time to note the relationships between the half-lives and the abundances, and to point out the real meaning of the logarithmic scales and have students do some sample calculations.
Because of the lack of background information, this applet by itself will not be useful as a tutorial.
Ease of Use for Both Students and Faculty
The user interface and controls are very clear and simple to use if the instructions are read. The output of the bar graphs is easy to see.
Users have to scroll to see the exponents of the numbers of atoms. Also, the fact that the half-lives are displayed only at the top of the data frame means that it is more difficult than it should be to relate half-lives to the bar heights. The default timesteps cause the animate to move too fast to be useful. The inability to see the total elapsed time makes quantitative calculations difficult, except in a step-by-step fashion.
Comments from Author:
Please note that the applet was written quite some time ago. Some of the issues regarding user interface are due to the fact that the Java language changed drastically over the past few years.