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 Feynman diagrams (Phillip "Flip" Tanedo, Cornell University/USLHC Collaboration) and quantum electrodynamics (QED) (Christopher "Bot" Skilbeck, cronodon.com).
Warner Bros. Television (2007)
bigbangtheory.wikia.com/wiki/User_blog:Sheldon_Cooper_PhD/Pilot
Selected/edited responses are given below.
Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"Feynman diagrams show the interaction of matter particles and force particles. Their interaction is at the vertex of lines where there must be an arrow pointing into the vertex and an arrow pointing out of the vertex. A squiggly line represents a photon, it is placed at the intersection of these lines representing electrons and positrons. Electrons and positrons form photons when they interact."
"e+ is a positron, e- is an electron and the gamma is a photon. Positron has a left facing arrow, electron has a right facing arrow and photon is the squiggle line."
"Positrons annihilate electrons."
"In Feynman diagrams there are two kinds of lines: one straight with an arrow and one wiggly. There can only be connected pieces with on arrow going into the vertex and one coming out."
"We read the diagrams left to right. They represent particles like positrons, electrons and photons."
"I am feeling lost."
Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"The orientation of the diagrams is confusing. I do not understand the significance of these particles and forces moving in a certain direction over time."
"The more complicated Feynman diagrams were hard to understand. The rules are hard to keep up with, might need more examples in class."
"I think utilizing the diagrams in a useful way is challenging to me."
"What internal/virtual particles actually are."
"How to draw them and how to interpret them. The diagrams just look like particles bouncing off each other creating photons."
"I found the interpretation of the diagrams to be a bit confusing at first but it got better with more practice. The only issue is when there are multiple interactions trying to see the big picture of what is being told."
"Pretty much all of it. I was understanding it at the very beginning, but then towards the middle/end I got completely lost and my brain couldn't handle any new information."
"It is all very daunting but with some practice it seems possible to understand. For right now how to draw one is clear but everything else that goes with understanding this type of diagram is beyond me."
"I'm struggling. Please help."
"The Feynman diagrams are a bit confusing. Some review on them would be really helpful."
"The reading was straightforward."
When reading Feynman diagrams, time runs from:
bottom to top. * [1] top to bottom. *** [3] left to right. ******************** [20] right to left. * [1] (Unsure/guessing/lost/help!) ******* [7]
Describe how the path of an electron and the path of a positron are drawn differently on a Feynman diagram. (Note that both paths have the same "e" labels.)
"The electron moves from left to right and the positron moves from right to left."
"Electrons have arrows pointing left to right, positrons right to left."
"I'm not sure."
"I'm struggling. Please help."
"I will be getting back to this after Wednesday. "
Describe what will happen if an electron meets a positron.
"Explosion."
"They annihilate each other."
"They destroy themselves mutually."
"A photon is formed."
"Annihilation occurs and a photon is emitted, which could later creates a new electron and positron."
absorbing a photon. ** [2] emitting a photon. *********************** [23] annihilated by a positron. * [1] (Unsure/guessing/lost/help!) ****** [6]
absorbing a photon. **** [4] emitting a photon. ***** [5] annihilated by a positron. ******************* [19] (Unsure/guessing/lost/help!) **** [4]
absorbing a photon. ********************* [21] emitting a photon. ****** [6] annihilated by a positron. [0] (Unsure/guessing/lost/help!) ***** [5]
"Must have one arrow going into the vertex and one arrow coming out of the vertex."
"The particles cannot go on the same direction where they meet the vertex. One must be going away from the vertex."
"Two electrons cannot form a photon."
"Both arrows are going in when it needs to be going in and then out."
"It violates rule 2 for Feynman diagrams, which follows a theory of quantum electrodynamics. It is an incomplete diagram of annihilation, matter and antimatter colliding."
"The electrons are both annihilated which is inaccurate?"
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I was confused on what exactly a photon is. Like is it just energy?" (Yes, in particular a form of energy that also carries momentum with it, and travels at the speed of light.)
"Feynman diagrams are confusing, yet interesting."
"The images really confused me, I think going over these GIFs would be helpful too!"
"I like these diagrams so far! I like how it is pretty easy to tell a story."
"Hi P-dog, I am sorry I have a chemistry midterm on Tuesday before our physics midterm and I have spent all of my time studying for that :/."
"I found this video from PBS to be very helpful in understanding Feynman diagrams, if you would like to share it." (This is great, just be aware that they are using the convention where time runs from bottom-to-top rather than from left-to-right.)
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