光为什么会「变慢」？费曼讲折射率

3Blue1Brown visualizes Feynman's lecture on the refractive index, explaining why light appears to slow down in glass and why the effect depends on color. It builds the idea from waves produced by oscillating charges in the material.

Why HN likes it: HN considers it among the clearest accessible explanations of what refractive index actually is and how light moves through transparent matter.

“probably the clearest reasonably accessible explanation of this topic anywhere to date”