Ben (narrator/author of the LessWrong post)
👤 SpeakerAppearances Over Time
Podcast Appearances
Momentum of light in glass.
I think that most people underestimate how many scientific mysteries remain, even on questions that sound basic.
My favorite candidate for the most basic thing that is still unknown is the momentum carried by light, when it is in a medium, for example, a flash of light in glass or water.
If a block of glass has a refractive index of, here's a formula, then the light inside that block travels, here's a formula, times slower than the light would in vacuum.
But what is the momentum of that light wave in the glass relative to the momentum it would have in vacuum?
In 1908 Abraham proposed that the light's momentum would be reduced by a factor of.
Here's a formula.
This makes sense on the surface.
Here's a formula.
Times slower means.
Here's a formula.
Times less momentum.
This gives a single photon a momentum of.
Here's a formula.
For omega the angular frequency.
Here's a formula.
The speed of light and.
Here's a formula.
The reduced Planck constant.