TOK physics: Feynman diagrams
Knowledge questions
If you understand a model do you understand the concept it is modelling?
Is a model useful even if it bears little resemblance to the process the process it is modelling?
Can models be a hindrance to the proper understanding of a concept?
Feynman diagrams are use in particle physics, they are quite simple and governed by strict rules, here is an example.
This is called a vertex, the way it is drawn is determined 2 rules.
- There are always 2 straight lines and one wavy line.
- There is always one arrow entering and one leaving.
- Time progresses from left to right.
- There must be something at the start and something at the end.
Applying these rules we can see that there are many other versions of this diagram. Try drawing 4 other possible variations.
Here are 2:
Why are the following not possible?
1. nothing at the end.
2. two arrows leaving.
3. two arrows leaving.
4. no wavy line.
More complex interactions can be represented by joining vertices.
This can also be spun around to give other possibilities, this is very useful, if one is possible all are possible. Using Feynman diagrams we can predict interactions. Predict 2 more interactions based on this diagram.
Here is one:
You now understand the model but don't know what it relates to, is there any point in knowing this?
This video will put them in context.