THE VIDEO SHELF · refractive index
Why does light slow down in water?
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 HN readers recommended it
HN commenters link it to correct the widespread misconception about why light slows in a medium.
This is a summary from the source dataset, not an endorsement by Hacker News or the video creator.
Video & recommendation details
- Creator / channel
- Fermilab
- Topic
- refractive index
- Format
- explainer
- Level
- general
- HN recommenders in dataset
- 3
- HN mentions in dataset
- 4
- Recommendation years in dataset
- 2020–2023
These counts and years describe the included Hacker News records; they are not YouTube views or the video’s publication date.
From the original HN conversations
Excerpts from the recorded comments. Follow each source for the full comment and surrounding discussion.
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: [VIDEO]
gugagore on Hacker News · 2020-12
In Well, Actually – Physics AnswersI 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. [VIDEO]
djmips on Hacker News · 2023-01
In Ask HN: Concepts that clicked only years after you first encountered them?For anyone who's interested, Fermilab has done several videos on this topic as well that I found highly informative: [VIDEO] [LINK]
gcanyon on Hacker News · 2023-12
In What is a zero refractive index material?
Summaries, classifications and recommendation records are from the HackerTube source dataset. Read about this library and its limitations.