Cuesta College, San Luis Obispo, CA
Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.
The following questions were asked on reading textbook chapters and previewing presentations on radioactive decay rates.
Selected/edited responses are given below.
Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"Radioactive decay as a whole interests me. We spent a large portion of CHEM 201B on it so it will be interesting to see it from a physics perspective."Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I thought that is was super interesting the probability of a given single M&M™ being eaten in a given time interval was not 0.5 and I can't explain why. :-( It caught my attention and boggled me."
"It was interesting to read about the radiocarbon dating because it offers such important data to our past."
"How independent identical (but unstable) nuclides are of each other."
"I thought that it was interesting how we will not be able to use carbon-14 as a way to date things in the distant future because we burn so much fossil fuel."
"The difference between the half-life and exponential decay expressions was a little confusing to me."What is the mathematical relationship between τ and half-life for radioactive decays?
"It will be confusing looking at it from physics instead of a chemistry perspective because I spent so long learning it for chemistry! There are a bunch of new terms for stuff!"
"Where the equations come from are confusing, and why there is a natural logarithm within the half-life equation is still confusing to me."
"I was confused by quantum mechanical tunneling explaining radioactive half-lives for alpha decay. I'm not sure what is meant by tunneling or how it occurs."
"It will be confusing looking at it from physics instead of a chemistry perspective because I spent so long learning it for chemistry! There are a bunch of new terms for stuff!"
"I have to wonder how this model applies to something like depleted uranium. Depleted uranium munitions are thought to be part of the cause of 'Gulf War Syndrome,' which affects veterans of the first Gulf War, and even civilians from Iraq and Afghanistan from the current Gulf War. Depleted uranium comes mainly from spent nuclear fuel, and is valued as a munition for being denser than even lead. Supposedly, DU is melted and cast into munitions. How will this affect its half life and effect on human exposure?"
"τ is the decay constant while the half-life is the probability of decay per the unit time."Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"τ is double the half-life."
"T1/2 = τ·ln(2)."
"I liked the expression of using M&M™s to explain radioactive decay, but I didn't quite follow it. Everytime you toss them, some flip "m"-up and some "m"-down, but it is not necessarily even. The odds are sporadic and unpredictable. Radioactive decay is predictable, right?" (Only in the limit of a sufficiently large sample of unstable nuclei. If you were given only one unstable nucleus, knowing its half-life would only give you a probability of it decaying for the current time interval, regardless of how many time intervals it has survived up to present.)
"Can you go over why radioactive decay happens? Or what initiates it?" (That will be the top of the next presentation, but the short answer right now is that it has something to do with Jenga® and Ellen DeGeneres.)
"How hard is Midterm 2 compared to Midterm 1?" (About as difficult as quizzes 4-6 were to quizzes 1-3.)
"This is hard! There are only there weeks left in the semester!" (What?!? This is supposed to be the easy, fun stuff.)
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