If light travels at the same speed in all media, then in what terms is it slowed down or sped up in refraction?
In: Physics
I’ll try to ELI5 this, but it’s quite complicated. Light does effectively travel slower in different materials compared to a vacuum.
Light is an electromagnetic wave, its got an electric field and a magnetic field which oscillates. When light passes through a medium, this oscillating wave causes the electrons in the material to also oscillate – an oscillating electron in turn produces their own waves. This doesn’t happen perfectly in sync with the light wave, so the wave from the electrons is slightly behind the light wave. When you sum together all of these waves the “phase velocity” adds up to a slower speed than the speed of light in a vaccum. The confusing bit is the propagation of electromagnetic forces is still happening at the speed of light in a vaccum, but the time it takes for the wave to enter the object and leave the other side is longer than in a vacuum. Unfortunately I can’t think of a good analogy!
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