gcanyonDec 2023Recommends
For anyone who's interested, Fermilab has done several videos on this topic as well that I found highly informative: ▶ this video [link]
in “What is a zero refractive index material?” · View on HN
Why does light slow down in water?
Why does light slow down in water? on HackerTube: recommended by 3 Hacker News commenters across 3 separate months, 2020–2023.
Fermilab
Open on YouTubeexplainer · evergreen
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.
Why Hacker News recommends it
HN commenters link it to correct the widespread misconception about why light slows in a medium.
- people recommended it
- 3
- separate months
- 3
- strong recommendations
- 0
- discussed on HN
- 2020–2023
“See this video for an explanation of why light travels slower through a medium with an index of refraction greater than one.”
What HN commenters said
4 Hacker News comments link this video. Each one links back to its thread.
djmipsJan 2023Recommends
I had thought because light was absorbed and re-emitted but that and scattering ideas are incorrect. See this video for an explanation of why light travels slower through a medium with an index of refraction greater than one. ▶ this video
in “Ask HN: Concepts that clicked only years after you first encountered them?” · View on HN
gugagoreDec 2020Recommends
For a video to address this misconception of the speed of light being constant, and it just appears to slow down due to ping-pong, I recommend "Why does light slow down in water?" by Fermilab: ▶ this video
in “Well, Actually – Physics Answers” · View on HN
vecterDec 2020Cites it
> Well, actually, the speed of light is constant, it just takes time to ping-pong around a lattice/gas. Photons hit particles, get absorbed, and re-emitted, which causes an effective slowdown at a larger scale. A gas is just vacuum with particles floating around in it. When photons travel between those particles, they are traveling at c. The effective slowdown is determined by the lattice/gas, and we denote this slowdown with the refractive index... This is wrong. Two sources [0][1]. [0] ▶ this video [1] [link]
in “Well, Actually – Physics Answers” · View on HN
Topics & tags
Fundamental physicsEveryday physics & science demosspeed of lightopticsphysics misconceptionswave mechanicsrefraction