4 ms·

> Light moves significantly (47%) slower through optical fiber than through space The what? As far as I know c is a constant.

• akalin 6y ago
  c is the speed of light in a vacuum
• kibwen 6y ago
  The constant c is the speed of light in a vacuum. Different mediums have different speeds of light within them; in fact, it's actually possible for light to not be the fastest thing in a given medium (for more precise definitions of all those words): https://en.wikipedia.org/wiki/Cherenkov_radiation https://en.wikipedia.org/wiki/Cherenkov_radiation
• busterarm 6y ago
  When you refract light, you change its speed, slowing it down. https://en.wikipedia.org/wiki/Refractive_index#:~:text=The%20refractive%20index%20can%20be,of%20that%20light%20in%20vacuum https://en.wikipedia.org/wiki/Refractive_index#:~:text=The%2.... https://www.zmescience.com/science/physics/how-to-slow-trap-light/ https://www.zmescience.com/science/physics/how-to-slow-trap-...
• sannee 6y ago
  Altought the answers so far posted are not exactly incorrect, it is also important to note that the geometry (that is, a cylinder for optical fibers) of the waveguide used influences the group velocity of the propagating electromagnetic field. This will always end up being slower than a plane wave in the same material, usually only somewhere between 10%-90% (and this also depends on the wavelength) of the free-space group velocity.
• RJIb8RBYxzAMX9u 6y ago
  In a vacuum. See Cherenkov radiation[0]. [0] https://en.wikipedia.org/wiki/Cherenkov_radiation https://en.wikipedia.org/wiki/Cherenkov_radiation
• pmlnr 6y ago
  Downvotes are unfair; this part of physics I either forgot, or never learnt, I can't tell. Thanks to those who pointed me at links.