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QED Knowledge Check

Test your mastery of the core principles.

Question 1 of 4
How does Feynman explain the partial reflection of light from a glass surface?
Explanation: Feynman uses the stopwatch vector model to explain how amplitudes combine to yield reflection probabilities.
Question 2 of 4
Why does light appear to travel in a straight line according to QED?
Explanation: The straight-line path represents the region where neighboring quantum histories reinforce each other constructively.
Question 3 of 4
What are the three fundamental actions of quantum electrodynamics?
Explanation: Feynman reduces all complex interactions down to photon propagation, electron propagation, and vertex coupling.
Question 4 of 4
What is the significance of the fine structure constant ('e' or ~1/137)?
Explanation: The coupling constant determines the probability amplitude for an electron to emit or absorb a photon.