Cuesta College, San Luis Obispo, CA
The Feynman diagram (A) correctly shows an electron capture decay process, where a proton and an electron interact to convert into a neutron and a neutrino. Discuss why the other Feynman diagram (B) showing an antineutrino interacting with a proton to convert into a neutron and positron is incorrect. Explain your reasoning using the properties of Feynman diagrams, particles and antiparticles, and interactions. Solution and grading rubric:
- p:
Correct. Discusses (1) how the second Feynman diagram violates the in-out path vertex rule, and/or (2) draws a corrected Feynman diagram for an antineutrino and proton respectively turning into a positron and neutron after the interaction. - r:
As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. - t:
Nearly correct, but argument has conceptual errors, or is incomplete. - v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. - x:
Implementation/application of ideas, but credit given for effort rather than merit. - y:
Irrelevant discussion/effectively blank. - z:
Blank.
Sections 30882
Exam code: finalpL3x
p: 16 students
r: 1 student
t: 5 students
v: 3 students
x: 2 students
y: 1 student
z: 2 students
A sample "p" response (from student 1408):
A sample "x" response (from student 8325), with at least some demonstration of understanding charge flow conservation:
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