Editing Refraction (section)

===Slowing of light===

As described above, the [[speed of light]] is slower in a medium other than vacuum. This slowing applies to any medium such as air, water, or glass, and is responsible for phenomena such as refraction. On the other side of the medium its speed will again be the speed of light in vacuum, {{mvar|c}}.

A correct explanation rests on light's nature as an [[electromagnetic wave]].<ref>[https://m.youtube.com/watch?v=CUjt36SD3h8 Why does light slow down in water?] - [[Fermilab]]</ref> Because light is an oscillating electrical/magnetic wave, light traveling in a medium causes the electrically charged [[electron]]s of the material to also oscillate. (The material's [[proton]]s also oscillate but as they are around 2000 times more massive, their movement and therefore their effect, is far smaller). A moving [[electrical charge]] emits electromagnetic waves of its own. The electromagnetic waves emitted by the oscillating electrons interact with the electromagnetic waves that make up the original light, similar to water waves on a pond, a process known as [[constructive interference]]. When two waves interfere in this way, the resulting "combined" wave may have wave packets that pass an observer at a slower rate. The light has effectively been slowed. When the light leaves the material, this interaction with electrons no longer happens, and therefore the wave packet rate (and therefore its speed) return to normal.