Why Glass Is Weirder Than You Think” — Feynman on Transmission

You look through glass every day. You've probably never questioned why it's see-through, or why your faint reflection stares back at you at night. But here's what's strange: the amount of light glass reflects isn't fixed. It depends on how thick the glass is, cycling between 0% and 16% in a pattern so bizarre it stumped Isaac Newton and broke the wave theory of light. The real answer comes from quantum electrodynamics — and it's weirder than you'd expect.In this video, we explore Feynman's famous analysis of partial reflection by glass, drawn from his legendary QED lectures at UCLA (1983) and the Auckland lectures (1979). This was one of Feynman's favorite examples for demonstrating how quantum mechanics works at the most fundamental level — starting with something everyone takes for granted and peeling it apart layer by layer.Uploaded 11-02-26📚 SOURCES:Richard P. Feynman, "QED: The Strange Theory of Light and Matter," Princeton University Press, 1985. (Chapters 1 and 2: "Photons — Corpuscles of Light" and "Fits of Reflection and Transmission — Quantum Behaviour")Richard P. Feynman, Robert B. Leighton, Matthew Sands, "The Feynman Lectures on Physics, Volume I," Addison-Wesley, 1963. (Chapters 26 and 31: "Optics: The Principle of Least Time" and "The Origin of the Refractive Index")Richard P. Feynman, Robert B. Leighton, Matthew Sands, "The Feynman Lectures on Physics, Volume III," Addison-Wesley, 1965. (Chapter 1: "Quantum Behaviour")Isaac Newton, "Opticks: or, A Treatise of the Reflexions, Refractions, Inflexions and Colours of Light," Book II, Part IV, 1704.Sir Douglas Robb Lectures (QED), University of Auckland, New Zealand, 1979 (filmed).Alix G. Mautner Memorial Lectures, UCLA, 1983.🎬 CREDITS: Script concept and production by this channel Inspired by the public lectures and published works of Richard P. Feynman AI-generated voice and visuals⏱️ TIMESTAMPS: 00:00 — Why would a photon care how thick the glass is? 02:45 — The 0%-to-16% mystery Newton couldn't solve 07:30 — "Fits of easy reflection" — Newton's desperate guess 12:15 — Wave theory to the rescue… and then it breaks 18:40 — Turning down the light: the click that changes everything 24:10 — Little arrows and the sum over all histories 31:00 — Why the interior of the glass contributes nothing 36:20 — Why glass is transparent (and blocks UV) 42:05 — What actually slows light down inside glass 47:30 — The photon that "knows" about the back surface 53:15 — Where the 4% comes from — chasing it to the bottom💬 One thing to think about: if every photon truly explores every possible path through the glass, what does it even mean to say a photon "went" somewhere? Drop your take below.
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