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Why does light slow down in water?
Fermilab
Fermilab's Don Lincoln explains why light travels slower in water and glass. He knocks down common wrong explanations such as absorption and re-emission, then gives the wave-mechanics reason tied to refractive index.
HN commenters link it to correct the widespread misconception about why light slows in a medium.
4 Hacker News mentions · 2020–2023