Online reading assignment: Feynman diagrams

Physics 205B, spring semester 2013
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 presentations on Feynman diagrams (Phillip "Flip" Tanedo, Cornell University/USLHC Collaboration).

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.
"To be able to see the different interactions through the diagrams was interesting. The diagrams and the rules for drawing the diagrams seemed easy, I just don't exactly get what it's used for."

"I think that this is a fun physics game."

"I like how a positron, mathematically, can be taken as an electron moving in reverse."

"Feynman diagrams are interesting that they are able to depict so much with a very basic diagram, it is helpful for us visual learners."

"I thought that it was super-interesting to see the arrows do not indicate the direction of the particle in space, but the type of particle."

"I like how this section overlaps the material im learning in nuclear chemistry."

"Finding out the pattern for the Feynman diagrams, it took me awhile to get the arrows and curved lines going up or down."

"I think the diagrams are really interesting, particularly how simple they are to draw without any knowledge of physics. It becomes complicated when you have to interpret what they mean!"
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The point of the diagrams were confusing. The readings said that there will be math introduced later on and am confused to what we are going to apply this to."

"I'm confused with virtual particles. I'm not really sure what they are or where they come from."

"I was confused by the arrows for a while and was reading the diagrams in the direction of the arrows, but they are read left-to-right. Once I started doing that the whole thing made much more sense."

"I don't understand how a particle can be moving forward in space but moving backward in time."

"I have a feeling that I am confused but I have read the article a couple of times that I have convinced myself that I am right. Then do positrons travel backwards in time?"
Describe how the path of an electron and the path of a positron are drawn differently on a Feynman diagram.
"An electron is drawn as a straight line with the arrow pointing to the right whereas the positron diagram is the same but the arrow points to the left."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"What's the average on Midterm 2?" (You haven't even taken Midterm 2 yet. For what it's worth, last year's class had an average and standard deviation of 51.3 ± 10.6 out of 75 points.)

"Are you confident the class as a whole will do well on the midterm?" (I for one am pretty confident. But I can't say that for the rest of you.)

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