Cuesta College, San Luis Obispo, CA
The Feynman diagram shown at right depicts: (A) an electron absorbing a photon, then emitting a photon.
(B) an electron emitting a photon, then absorbing a photon.
(C) a positron absorbing a photon, then emitting a photon.
(D) a positron emitting a photon, then absorbing a photon.
(E) pair production, then annihilation.
(F) annihilation, then pair production.
Correct answer: (A)
Since time runs from left-to-right in this Feynman diagram, an electron (which is traveling left-to-right) absorbs a photon in the first vertex, then at the second vertex this electron emits a photon. (N.b. This is a Feynman diagram for Compton scattering.)
If the time axis were instead diagonally lower-left-to-upper-right (which is not the case here), then a photon would create a positron and electron pair, of which the electron would later meet up with another positron, annihilating each other to produce a photon.
Section 30882
Exam code: quiz07f3yN
(A) : 23 students
(B) : 3 students
(C) : 0 students
(D) : 1 student
(E) : 3 students
(F) : 2 students
Success level: 72%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.36
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